Model diagram add relationship path

Model diagram add relationship path

Hello,

How is it possible to add a link in the model diagram (a new path between 2 data tables) ?

In attachment the link exists for the dates (in green) but I would like to link "user" to "visits report owner" (see red link).
I cannot add a path in "configure lookups"
I tried to do a test with including a new application copy in 3rd picture and that's actually what I need.

how is it possible to add a new path ?

Thank you