So, i want to make a speedrun category on "ROBLOX: get a snack at 4 am" but i dont know how to do it. Can anyone help me?

Copying from the thread you necroed that you should've read Only game moderators can add new categories. Ask for a new category in the forums of the game ask in their discord, or contact the game moderators directly.

Or, if this is technically a new game, there's a different process you can ask them about