Thanks! for your response
It was the mining keybind I was looking for indeed to remove bricks pavement and ghosts. I gave it another binding. so I could use right mouse like I want it for a while until new insights probably.
hi in 0.17.69 I use default shift left click: placing a ghost building alt right click: removing a ghost building reservation
I can't find the second (removing) key binding in >settings >controls (or I overlooked it). (I would like to sometimes use right mouse click for unselecting (q). Apparently ...