I noticed that there are plugins/parts/behaviors that might need to catch up to the new 3D features. I'm unsure where to post this though since it's not a bug, and imo not exactly a simple feature request either, so I'm posting it here. Feel free to add to the list if I'm missing something.
Obviously this is a huge chunk of work, I don't expect this to be complete any time soon.
I have ordered these in terms of what I believe to be the least amount of work.
Sine
Still says it uses Z-elevation which was deprecated (I'm assuming it's just using Z in the background but it's named wrong)
Tween
Cannot tween 3D rotation property
Drag & Drop
Does not fully work with 3D camera/always takes the top instance in terms of Z which could be simply incorrect. Maybe this could be solved by adding a "Start dragging [instance]" action?
Bullet
Does not support 3D bullet movement
MoveTo
Does not support Z movement
Turret
No 3D turrets supported.
Orbit
3D orbits
Layouts
Wouldn't it make sense to also be able to specify a layout depth? If yes, the "bound to", "wrap" and "destroy outside" behaviors would also need to be updated.
Tile Movement
3D tile movement
Custom movement
(Imo not too important, I doubt this behavior sees much usage in general)
LOS
3D Line of Sight and 3D raycasting
Pathfinding
3D pathfinding
Physics
Box3D? Either way this would probably have to happen before the rest below
Car
3D car sounds fun, but not supported
Platform
Finally, Super Mario 64