Hello [IliaLazarevskii] !
I've created 1 extra lookup column and routing it on my existing one with those parameters below
It show the contact depending to this supplier.
Then, I'm asking if I can set an "add new" option and customize the corresponding form. Cause with the actual "add new" form by default, you have the chance to change every SP field, that I totally don't want to.
So, do an user can change only "supplier contact" whan not existing ? I saw this : Different Form Set on Add New Item - Forms - Plumsail Community
But I'm asking is I can create a new form posted into "all users" group, dont' know if it's possible here cause NEW EDIT and DISPLAY already exist.