Hi Sebastian,
In the associationtables you cannot add any attributes yourself.
For your use case you have 2 options:
The option to do this is to manually create a mapping table yourself if you want to store extra information on the association. So f.e. you would get User → UserEmployee → Employee as entities. This would create 2 EXTRA tables (1 extra mapping table and 1 extra table that is adjustable with attributes.
Another option is to have 2 associations between the entities, in which 1 is for the “active” version and the other one is for all. But this will still create an extra table as each association is a table in itself.