Addon with an object / multiple reference

Hello!

I want to make an Addon of a table column that is an object. I don't know how to do it or what to type in the route. (see screenshot)

I have a table of users that has a connection to a 'competences' table. So a user can have multiple competences assigned to him. I know how to do it with only a single reference, but not with a multiple reference (object).

Can someone help? Thanks!
[Bildschirmfoto 2022-02-28 um 16.18.01.png][Bildschirmfoto 2022-02-28 um 16.16.29.png]