Relationships between tables in a custom module?

Question

1C-Bitrix

The bottom line is that you need to create a many-to-many table relationship in the Bitrix module. Example:
Users: Items:
1 Matan
2 History
3 Informatics
4
is obtained in order not to constantly duplicate information for each user, a directory is created Items and looks like connections of the type
User - 1 Matan History
User - 2Matan Informatics
User -3 History Informatics
It’s not difficult to create an intermediate table, I can’t figure out how to embed adding objects to each user in terms of visualization
I didn’t find such things from the documentation, and for some reason I didn’t see similar modules

Answer 1

element property?

Answer 2