probably you are one of those who thinks 'why the hell there is no undo in hotglue?!'...
you know what? there is! it is just not called 'undo', but 'revisions'. also, it does not work exactly like 'undo' (because it isn't) but even better allowing you to come back to versions from the far past.
(i'm guessing in other software it is called 'history')
'revisions' are available in double-click (global) menu. try it!