ctrl z undo by mistake - how do I get rid of all the x's?

[ExoneratedPhoenix]

I am learning all the key bindings and did a few ctrl z's on my belts.

I can't find anywhere online to get rid of them. A few placed claimed ctrl-shift z, but this just made more red x's and undo's....

[KatherineOfSky]

Xs are caused by using a deconstruction planner. To undo deconstruction, press Shift while click-dragging the deconstruction planner

[Derpykat5]

If you don't have a deconstruction planner, press alt+d