The current field must match the join key '|' in the table that serves as the 'one' side of one-to-many relationship. Enter ...

The current field must match the join key '|' in the table that serves as the 'one' side of one-to-many relationship. Enter a record in the 'one' side table with the desired key value, and then make the entry with the desired join key in the 'many-only' table.