Really late response, but Category Extensions are something we plan to add officially. There still isn't an ETA for it aside from When It's Added(tm), but there'll be an update in the News section here and the KFL channels in the speedrunning Discord when it is.

We had an unofficial document as a sort of leaderboard for this when the demo released, but before the full game's release. Like with Star Allies before it, though, there's really not much demand for a "Demo%" now that the full game's out, especially two months in. If it showed up at all, it'd likely be as a category extension and even then, it's admittedly really unlikely.

When you submit a run, you'd simply put a link to your image where it says "video." As long as you use something like Imgur for the image link, it'll show that when viewing the submission.

The image you'll want will look something like this:

What others have already said; moderating/verifying is a volunteer thing and we have other stuff that goes on in our lives alongside sorting things out with the game's leaderboards. We do get to the runs sooner or later regardless, so just remain patient.

If I may interject a bit, as I tried to humor this for the sake of seeing if it could be done: Short answer is that it can't.

Powerless/Abilityless is entirely impossible as at the last room of Chapter 3 in Revenge of Meta Knight, you're required to use Fire to light a cannon's fuse. The one beside it, which has a switch to ignite it without the need for an ability, is a fake and damages you. Unlike the Meta Knight fight in Kirby's Adventure or its remake, Nightmare in Dream Land, this ability isn't forced on you in any fashion beyond the puzzle giving a big glowing hint that you need to light a fuse. Also unlike the aforementioned fight, the ability is also able to be tossed as soon as it's used, compared to being stuck with it for the entire fight. Since it doesn't "make" you use it and calling a Helper would also be against the rules since you need an active ability for that, you'd be stuck and unable to progress further. The only exception for the Helper bit is maybe the end of RoMK where you're forced into riding Wheelie, but that'd only apply if you can't just jump off it and dismiss it as soon as you're given control of Kirby again.

As for Floatless, you'd have to use Beam to get past the very first raised platform in Spring Breeze. I'll let that speak for itself as to why doing both together wouldn't be possible at all. Regardless, Kinnin11's right in that it'd need to have popular demand for it to have a leaderboard, but don't let that stop you from trying to run it for your own enjoyment.