Is there a way that we could split the single level speedruns in 3 different lists? I think it is a bit much with nearly 40 Level in one list

Sadly I don't think there's a good way to do that in sr.c, you'd either have to

a) create separate pages for the expansions (which would require new "games" to be approved and would be even more unwieldy), b) lump the missions together into a "category" with "subcategories" (which would be even more unwieldy and would keep the runs from appearing on the overview), c) use names like "mission 1" through "mission 16" and stack the original/expansion/legends missions onto the same rows (which would make their names disappear on the overview), or d) move the level leaderboard to a google sheet (which seems like overkill, the board is nowhere near as bad as it was in super mario 64)