Ctrl-z (undo) while holding last detached assembly and attempting attach as new radial addition cause instant quit, crash.
Because building anything, multiple stacks, is easiest done on the center node. So I build a stack of six __ with a LTV-45 on the bottom of a MK-1 with a heat sink and KERR parts(since rocket science is not random chance,) three goo containers, 2HOT Themoeter, and barometer. Disconnect it hit ctrl-z while still having it selected, and the part is now red "ghosted" selection, and the original part is back where it started. Now I hit xx to make a triple radial, or it is already set to it, I mouse over the side of the original and three appear radials appear. I click to install and blip, the program closes instantly and Steam does a sync. Its faster than X the application window or of course menu quitting.