okay i tried it again, you are right.
and i think i found what was confusing me.
undo only works if you havent touched any parameters or entered new trigs.
i just cleared a sequence, and undo works fine, no FUNC holding needed
but if i touch anything thats not undo command after a clear, undo doesnt work anymore.
EDIT: its confusing that undo doesnt work if you go to a different page, even without changing any parameters or entering new trigs. Which is why i never used it because you only notice that you made a mistake after you press a button or two, in which case its too late to undo.
Thanks everyone, now i know how undo behaves, maybe ill be able to make use of it. 
its nice to have that option.