There is an 'update_set' field on the 'sys_update_xml' table. I've had instances where I'm working with multiple update sets, and made a change to one module in the incorrect update set. I've simply gone into the record and changed the 'update_set' field to the correct update set.
You need to be careful, though, obviously, as you need to be aware of which changes have been made, as you don't want to move only a part of the change (i.e only one of two records). Otherwise, you'll end up with errors in preview.
Cheers,
Tim
