There's a couple different formats that can be used to organize these leaderboards. Each layout is shown. The first is on the BO1:Z and BO2:Z page and the second type is shown on the BO3:Z page.
I personally like the layout on the BO2 and BO1 pages but that might be own personal bias because I set those up. The largest downside is that it gets a little bulky with more runs and you can only see the first place.
For either of them, it doesn't look like you can nest the menus. i.e. you can't have it go TranZit->EasterEgg->Richtofen Ending->Obscure Misc category. You can, at most, have 1 layer down, like we have in BO3, The Giant and then PaP and the Easter Egg. The largest downside to this is it looks like it greatly limits the number of level types that can be had. It also looks like all Solo stuff gets lumped into Co-Op stuff where in the other layout it wouldn't. And it clearly makes a difference whether anything's done Solo or Co-Op.
That problem with nesting and size limit can be eased by using the system in BO2. The more levels you add, the longer that IL list becomes and it doesn't necessarily look cluttered by squeezing all the names together on one line. The list would just extend downward, if that makes sense.
I wanted to gauge what everyone thinks about this because it would be nice to have uniformity and group input on the direction to go. My vote is on the IL system, at least until proper nesting is in place (if that's on the site agenda).
EDIT: Actually, apparently there is nesting. Check out what I've done on the Full Level leaderboards side on the BO2 page. Looks pretty good, IMO...