I have 2 ideas to improve the hotbar, both wouldn't necessarily be needed together to enhance quality of life.
1. Have the F-Keys toggle to alternate hotbars. This way you can have F1 for building, F2 for power etc.
2. Make holding a shortcut key bring up a radial menu much like hold C, the options being other buildable items from that category in the Q menu ie. holding the button for a conveyor would show all the logistics items. Selecting an option changes the hotkeyed item like hitting the number.