xtom

With lots of mechanics might need to introduce them gradually over multiple levels. First level(s) should be easy, not too hard on the difficulty curve/frustration. Maybe checkpoints. I like the way that video has red barriers on some of the ends making the level not too difficult. What about a putty ball that splits in half if a saw hits it, or powerups that change from soft to hard ball to beat certain enemies or puzzles. So much you could do.

Maybe a turnstile/roundabout where you have to time your exit carefully. And some rubber walls that bounce you more. Didn't realize so many things could be added to a marble game.

Sounds good, maybe have a jump/bounce to hop over gaps and obstacles. And teleports to other parts of level.

I would prefer a collapse all option as it would make for less scrolling and easier to browse the scene tree in general. A right click move to filter option within the scene tree itself would be more intuitive and less disjointed to having it as a properties selection but I don't know what is possible and what isn't.

I use the filters, they are a very useful addition but still even when there are lots of objects under custom filters the suggestions mentioned here would also be very useful to have. Anything that speeds up map making/organising is good.