Undercut Items Scan
Not sure if this is possible or useful, but here goes:
Whenever I run a post scan, save all the items that have info "undercutting competition" into a new (temporary and invisible) group.
Add a button to the bottom of the post scan once all items have been posted to "Scan for undercuts" or similar.
This would then scan all the items you've just posted (with "undercutting competition info field" for previous auctions posted, basically a shortcut to cancel undercut items so you can bring them back to stock for posting again.
EDIT: An alternate way to do this may be IF numPosted > postLimit, add it to a list, and create a way to jump to a cancel scan on those items.
This feature already exists. Just click “Run Cancel Scan”.