At this moment, there is no other way to mark your FTF than tagging if you can not fit into single Bookmark list.
If it is very inconvenient for you to tag FTFs with a string in logs, you might try to ask for implementation of a feature that will allow to specify more bookmark list with FTFs (probably by editing the question to the category Feature Requests), but this is very rare problem affecting really just a few users so I don't think it will be a high priority against other features, ideas and requests that are on the way and that will help many more cachers around the world.