1) Is there a way in EE2 to restore a GUI object after it has been removed from the editor? I didn't select "Erase removed elements" yet.
2) Also, the UNDO when editing gui objects didn't work. When I accidentally removed a region, UNDO didn't bring it back.

Thanks!

Click the trash can icon on the top right of the explorer window to show the removed elements (removed but not erased). Right click a removed element and select the Restore option.

Thank you Rofar!

2) Perhaps you've made a second operation just after removing the Region, and the Undo was flipping between the second operation and no the removal itself.