@richard, can you make an inventory extension that works with the 3D rendering extension?
Have you tried mine?
As long as you set the Z index of the inventory sprite high enough, it should be able to draw on top.
You can also try looking for more extensions related to inventory in my Awesome Arcade Extensions list but I don’t think there are any more besides mine.
Can you make the same without only the bar?
And turn that into an extension?
You can forgo the hot bar by not making it in the first place.