I hope it's okay to chime in here, I have the same question. I'm in the Banking tab, looking at the categorized items. (I had already deleted all the rules from the uncategorized column). The majority of the categorized items  have "auto-add rule" in the rule column. What happens when I click undo in the action column? I'm coming in after my client who purchased and set up things without me seeing it first. I'm trying to start fresh. Thanks for any help!