I wanted the entry in the many-to-many relational field to be unique. When the user enters a duplicate record in the many-to-many relational field, BD will give the user an option to edit the entry. I wanted BD to jump directly to the record when the user chooses to edit the content of that record.
Just some thoughts. If you create a new record in M2M field with a button script rather then allow clicking in the M2M, then you have better control. BD will create a record set variable with the new record which means you can can always locate this record for futher actions (for each record loop action).
Another idea would be a time stamp on edit and sort M2M on this to make it first in list, which is accessable with a script (Edit MMR or may be lookup).
Keep in mind it is possible to add the "internal" record id to each record with a maths field set to the current record via recordset variables (current) and script run on comfirm etc). You then can access this record at any time using this stored field value directly - also handy as a unique value.