Hi,

thank you for your reply. No, it doesn't work, but I found a way.
If you put that domain in the current domain space, it gives you error. Probaby, since in Studio they want to make domain "easy" to build, they removed the possibility to put fields as values.
In order to do that, you have to go in technical part, in views, search for the right view and put the domain there.
It will work and when you go with Studio on that domain, it will say "this domain is not valid".

Hope this will help also future users.

Add the following condition to your domain on the opportunity field where partner_id on the right hand side is the field used for customer.

('partner_id', '=', partner_id)