X Y Z Axis Refrence
There is a small arrow on the grid that does give some idea of orientation , however it would be far more useful to have a simple diagram in one of the corners presenting the current orientation. Something like the way UE4 (image below) does it would work wonders and help people keep their models facing the intended direction.
Additive and Subtractive Mesh When you go to place an asset(model of any kind) if you could change whether it adds or subtracts that mesh to the scene it would allow you to make much more complex models without having to leave the engine. This would make the Primitives section much more useful as you could make nearly anything. This combined with the planned addition of being able to import your own models would mean you could make your model in asset forge, export it once you like it, re-import what you made and then have it as a drag and drop model to play with.
Right Click to Clear Mouse
When you select a mesh to be placed in the editor, if the Left Mouse is pressed the mesh is placed. It would be kinda nice to have the ability to Right Click to delete the mesh before it is placed, i.e. clearing the mouse.