I'm trying to understand the ask.
You are saying that this is your setup
Users < Publication Authors > Publications
and in addition on the Pubs table you have say 3 User fields and a list user formula field. So you have duplicate effort to have those 3 user fields on the pubs table and also that middle join table.
You seem to want to continue to enter the [Authors1, 2 3 etc] directly on the Pubs Table but auto create the join table records.
Is that the ask? If so, there is a pretty easy answer with Automations.
Basically I would set up an Automation that would trigger when a Pubs table record is added or modified or deleted and where the Authors were changed.
Step 1 would be to delete all the join table children related to that Pub.
Step 2 would be to add Author 1 child record into the join table.
Step 3 would be to add Author 2 child record into the join table.
Step 4 would be to add Author 3 child record into the join table.
Step 2 would be to delete any child join table record with a blank Author.
