Hey @KaKaRoTo idk if you care about 0.7.x stuff for furnace but. I had someone report an issue where, on 0.7.x, with Furnace Advanced Drawing Tools turned on, Multilevel Tokens would add its UI stuff twice into the drawing configuration
I did a bit of digging and the problem is this change in the Application._render() function in the foundry code
Since your FurnaceDrawingConfig inherits from DrawingConfig but sets its name to "DrawingConfig", the new Foundry dispatch code ends up calling the renderDrawingConfig hook twice
Caused by 0.7.x calling render hook on all base classes in the hierarchy
From
@grand
:Caused by 0.7.x calling render hook on all base classes in the hierarchy