Original Super Mario Bros. 2 has categories called Any% or all levels [character_name] only, so why can't it be created here too? As well as some (if not all) other categories from here https://www.speedrun.com/smb2ce I think they would fit this game.
Because we don't know if people will run it, which runs the risk of ending up with empty leaderboards. If you want it to be added then your best option is to do a run yourself first and then talk to the moderators.
I’d love to have Any% or All Levels Character categories as well. Can I just try them and send it to a moderator? How would I submit such a run? One possibility is to share a YouTube link to it?
These categories have now been added under the Misc. tab for now https://www.speedrun.com/sma#Single-Character