1. The Elements List, a feature as obvious as needed in complex designs. This implies elements' custom names.
2. Measure tool, like in MS 3D Builder, so I don't have to switch to it in order to measure some lengths (u need to do some gymnastics to measure them now).
3. Selective unhiding, so I dont have to hide back all those backup components after unhiding everything (elements list is the way).
4. Edges' (or elements') lengths disappear after a few seconds OR while I start pivoting (with MMB or RMB)... What for? Let me think or calculate the desired length, and let me pivot around without the need to constantly click the element's edge. Just make those lengths disappear only when I click (with LMB) somewhere else than the element.
5. Flexible element's height's (by height I don't mean element's Z length, but the distance from "ground" ([x,y,0] point)) DISPLAY, so I don't have to zoom out to change it while I am designing an element like 20cm above the "ground" level.