I started to test VfR3 once more and here an other example of UI optimization.
The current diffuse layer control look like this. Not needed, at the first place the opacity. Confusing - the multipliers are per default hidden in a sub menu. At the multiplier sub menu the texture maps are shown a second time.
Here a simplified version. Color and texture are placed at the same place. No sub menus. Screen space is saved, an better overview is possible, no options are hidden.
The roughness parameter is very seldom needed, it could be moved to the Advanced Options too. Also the Muliplier Mode could be moved to the advanced options, since very seldom needed too. So, we could get very clean and simple looking diffuse layer options and one sub menu for advanced and seldom used options. Is it not good looking? 
I would be very glad if UI suggestions would be taken in account.