Sorry, I should not have say this, I did try again, I'm getting slowly used to it. I think there's a lack of explanations in the handbook, I realized you could had many of those coloured ribbons you can mix as you want while moving them from left to right ! To realize you could move a ribbon took me ages !!!
Anyway, I didn't found the way to cancel the very last operation without having to cancel all.
Note that if you type "." as first typo, you get "Internal error - xf2-gsb : MassRenameForm"