Creating terrain manually and its not your guarden variety peaks , hills , valleys is very a rather complex design- and was wondering why the UNDO system isn’t working right ( or right and I’m not using it correctly?) .
I , say, do a flatten, and then when I try to UNDO it, it does a undo on a prior action, making it impossible to UNDO just the last step.
Is that a known problem that crops up the via more elaborate terrain designs or my not understanding completely how to use UNDO 
TY anyone-