Thanks for playing!
It is two distinct button presses... Left then Right for Destroy Newest and Right then Left for Clone Upwards. It was hard to convey that they were not at the same time, and it has confused other players as well. It also has to be done within a small time window (just under half a second).
I was pretty sure that was it when "Clone Upwards" showed up with the reverse pattern.
I dunno about others but the + between them makes it seem they are a combo (ie, Ctrl+Alt+Del) rather than a sequence to me. Also, I may be hitting them too fast and will try to make them more distinct to see if that helps. I'll try again in a day or three.
Thanks for the response!