If you've played the special edition with the new graphics, you'll know that using the inventory is a lot harder than with the classic graphics interface (not to mention the original game). However, Stan would say that this baby's LOADED with extras!
For instance... Did I tell you about the automatic item selection?
Whenever you open the inventory, you'll see one item gets a yellow border. That item will be selected if you press the enter key. You can control which item will be selected by opening the inventory, positioning the cursor on the item (so it gets the yellow border), and then closing the inventory. The next time you open the inventory, the yellow border will still be on that item, as shown in the item selection video.
So, for example, while walking to enter the circus, open the inventory pressing I (or Alt), position the cursor on the pot, and close the inventory pressing I/Alt once again. Now, when you have to give the pot to the Fettucini brothers, you can position the cursor on the place where they will be (do it right after Guybrush enters the circus), press I/Alt, press G (give), press Enter (to select the pot) and click on the brothers. The giving items video shows the result.
For hitting the right sequence with the keyboard, here's a small tip that is useful for me and might be useful for you. Right before giving the pot to the Fettucini brothers, you get idle time while Guybrush is saying "Of course I have a helmet". During that idle time, I mimic the movements of what I'm about to do. That is, I mimic opening the inventory with my thumb, selecting give (I use my ring finger for that) and then pressing Enter (I use the "F" key for this, so I use my index finger). Then, when the idle time is over, entering this key combination becomes easier because I've just practiced it.
Note that there's a small delay between the moment you select the item and the moment you can use it (maybe due to the time it takes the cursor to change from "inventory mode" to "interaction mode"). That means you might need to click with the mouse more than once after selecting the item. But don't click several times if you do this while Guybrush is still walking to the place where he's going to use/give the object, or the second click will cancel the action. In these cases, you usually have plenty of time, so wait a bit before clicking. The only place where this might be an issue is when giving the fish to the troll; in this case, open your inventory right after you start walking to the troll (as seen in the giving the fish to the troll video), or you will trigger a dialog.
This method isn't significantly faster than using the mouse (maybe a few tenths of a second in some places), but it's more consistent. And, after all, replacing two clicks with 4 consecutive inputs because it might save a couple of frames in a 45-minute run is exactly what speedrunning is about! Besides, if you use the mouse, trying to speed things up by positioning the cursor on the place where the element will appear before opening the inventory is tricky. If you open the inventory without moving the cursor, clicking on the item will do nothing (unless it already had the yellow border). You'll have to move the cursor again (even if it's one pixel) and then click on the item, which makes proper mouse movement even harder. You can check this annoying behavior in the failing to select an item video.
You can also position the cursor on the item you need before giving the meat with condiments to the poodles (while walking to the mansion, open the inventory, position the cursor on the meat, and then close the inventory), giving the breath mints to Otis (do it while walking back from the mansion), giving the fish to the troll (do it at the lookout point), using the chicken on the cable (do it at the lookout point), using the shovel with the X (do it while walking through the forest), using the mug with lock (do it while walking to the jailhouse), using the gunpowder with the cooking pot (do it after getting the ink), using the first rope on the strong branch (do it right after using the lens with the sun, before the dam explodes), giving the little idol to the cannibals (do it while exiting the clearing), giving the leaflet to the cannibals (do it while exiting the village after giving them the little idol), using the magnetic compass with the key (do it while walking to the ghost ship, after using the necklace), using the key with the hatch (do it after picking up the jug o'grog), or using the glob of grease with the door (do it after getting the glob of grease). The same principle simplifies using the ghostly feather with the sleeping ghost crew the second time around; no need to move the cursor back to the feather and back to the ghost.
Unless you have three hands, you'll probably need to configure your keyboard to take advantage of this feature. For example, I map my "F" key so it becomes "Enter". Another option would be using a mouse with 5 buttons and configuring one of them so pressing it is equivalent to pressing the Enter key.
But wait, there's more! Did I tell you about the automatic NEXT item selection?
When you get rid of an item, the item which followed it in the inventory will be the one that gets selected. This is particularly useful when giving the bananas to the monkey. After giving it the first banana, keep the mouse cursor on the monkey and press I/Alt, then G (to give), then Enter (to select the next banana) and then click on the monkey. You won't have to move the cursor at all. Repeat until you're out of bananas. For a demo, check the giving the bananas to the monkey video.
But wait, there's more! Did I tell you about the auto-scrolling?
When you get rid of the last item in your inventory, there's no "next item", so the item that will be selected will be the first one, meaning the inventory will automatically scroll to the top. This can be annoying in a couple of places.
The first one takes place at the end of Part II. After finishing the recipe, you hopefully don't forget to go back to the hatch to pick up more gunpowder, which means the gunpowder will be your last item. The fastest way to use the cannon is to first use the gunpowder with the cannon nozzle and then use the rope with the cannon. However, since the gunpowder was your last item, after using it the first item in the inventory will be selected and you'll have to scroll down before using the rope. So, instead, pick up the rope after you've finished the recipe and you've taken more gunpowder. This way the gunpowder won't be the last item and you won't have to scroll to use the rope. Moreover, after using the gunpowder, the rope will become the selected item, which is exactly what you need.
The second situation also has to do with ropes. When using the ropes in the crack, the order matters: use the one that appears first on your inventory or you'll have to scroll down the inventory before using the second one.
The good part is that we can use the auto-scroll to our advantage when adding the ingredients to the cooking pot in Part II. Instead of picking up the Jolly Roger at the beginning, pick it up right before going to the kitchen to add the ingredients to the cooking pot. Add the gunpowder, wine, cereals, ink and cinnamon and then the Jolly Roger. The inventory will scroll to the top, where you can easily select the map to get the flaming mass (if you do it earlier the Jolly Roger will no longer be the last item) and then add the chicken and the mints. Note that, given your inventory at this point, after using the map, the chicken will automatically become the selected item when opening the inventory (since the chicken was next to the map) and when using the chicken, the breath mints will become the selected item. That means you can use these items while keeping the cursor on the cooking pot.
These techniques will help you lower the time it takes to add the ingredients to the cooking pot in part II to a time similar to the one you get when using the classic interface. Check the cooking the recipe video for a demo of the whole process.
But wait, there's more! Did I tell you about the reverse item usage?
Just like in the original game, instead of using an item with the cooking pot, you can use the cooking pot with an item. The advantage of this approach is that the delay between selecting the item and using it is gone: press U (to use), click the pot, press I/Alt, press Enter, and you'll use the item immediately.
But wait, there's more! Did I tell you about the arrow-keys navigation?
You can also use the arrow keys to browse through the items. For example, when using the ropes in the crack in Part III. At this point, the last items of the inventory will be, in this order, a rope, the lens, and another rope. After using the first rope, walk to the sturdy stump, and then press U (to use), click on the sturdy stump, press I/Alt, right arrow (to select the second rope), Enter. The using the ropes with the arrow keys video shows these actions.
This technique is harder and slower than using the item that already has the yellow border, so you should try your best to have the item ready before using it. In this case, it is actually possible to open the inventory, press the right arrow to select the second rope and close the inventory immediately after clicking on the sturdy stump to climb down to it. This will make using the second rope easier, as shown in the selecting the second rope video, but the time window to open the inventory after clicking on the sturdy stump is very small, so you might miss it.
But wait, there's more! Did I tell you about combining some of these techniques together?
The fastest way to use an item is getting it ready (that is, making sure the yellow box will be on that item when you open the inventory) while Guybrush is walking. Sometimes, you'll have plenty of time to do so; for example, you can get the pot ready to use at any point between exiting the scumm bar and talking to the Fettucini brothers. But, sometimes, you won't have much time. In these cases, you should use the arrow keys to get an item ready while Guybrush is walking and you move the mouse to the place where you're going to do the next action.
The first time this happens is when giving the gopher repellent to Otis. Here's what you can do: get the breath mints ready while walking back to the mansion. Then, while Guybrush is walking to Otis' cell, open the inventory, press G (to give), Enter (to select the breath mints), wait a fraction of a second so the cursor changes to "interaction mode" and click on Otis. Immediately after that, open the inventory, press the down arrow key so the gopher repellent gets the yellow box, and close the inventory before the conversation with Otis starts. Now you're ready to go, as you can see in the giving the gopher repellent to Otis video.
You can do a similar thing in order to use the mug with the barrel. Before going to Stan's for the first time, make sure the yellow box is on the bottom-left item of your inventory (it should be one of the T-shirts). Then, while walking to the scumm bar after getting the note from the lookout, open the inventory, press the down arrow key so the note gets the yellow box and at the same time position the mouse cursor on the place where it should be on the next screen. Then, enter the scumm bar, pick up the mugs and, while you walk to the curtain and wait for the screen to scroll to the right, open the inventory, press the right arrow key (to select the mug), close the inventory, and start walking to the kitchen. Since Guybrush walks slightly faster than the screen scroll, you won't lose time for doing so, as shown in the using the mug video.
After finishing the recipe, pick up the pot, exit the kitchen and, while you're walking to the hatch, open the inventory and scroll down by holding the down arrow key. Then pick up the gunpowder and the rope. Now, while Guybrush is walking, open the inventory, press the down arrow key and then the left arrow key so the gunpowder gets the yellow box and, at the same time, move the cursor to the top right corner of the screen making sure that the mouse cursor does not enter the inventory window. The cannon to monkey island video shows the process.
Finally, to use the ghostly feather, start by getting the key and, while walking through the room with the sleeping ghost crew, open the inventory and hold your down arrow key until the key gets the yellow box and, at the same time, position the cursor where the ghostly feather will be in the next room. Then, pick up the feather, click on the passage so Guybrush starts walking towards it, open the inventory and press the right arrow key while, at the same time, you move the cursor so it will appear on the ghost's feet when entering the next room. The ghost ship video shows this and other things you can do during this part of the run.
But wait, there's more! Did I tell you about using an item as a reference to position the cursor?
Right after using the lens with the sun, open your inventory and select the rope, positioning the cursor on the bottom right corner of the box containing the rope. Doing so will not only make it easier to use the rope in the crack, but it will also position the cursor on the river, which you can click to get to the pond faster as shown in the getting to the pond video.
But wait, there's more! Well, not really. I think you can live without this particular piece of junk.
The Tab key does the same thing as the mouse right button, meaning that, after positioning the cursor on an item and using the keyboard to select "Use [item] with", you can press Tab to finish the command. However, if you press Tab between the moment you select the item and the moment you can use it (the delay mentioned earlier), the action will be cancelled, so it's not really worth it.
You can watch all the videos mentioned here in the new graphics inventory tips playlist. Make sure to check the video descriptions, though, since the videos themselves don't contain captions or explanations of what's going on.