Bring back last clipboard?

An undo function of sorts that brings back the las blueprint in case it's cancelled by mistake using right click. could also work for placement (undo last placement, like a ctrl+z.)

Yes. The last thing placed should always be placed in a buffer to allow one to paste it again if needed.

Add a key binding to go back to previous selection with a settings, configurable history of selections (maybe you copied a few machines and pipes, accessed a blue print, pasted a blueprint and want to paste again, or cut some machines and want to recover what you cut, etc)
Related: Add a binding to cycle through a history last selected objects