Hi!
You can use the ‘constrained by’ option from the ‘Selectable objects’ section of the reference set selector: https://docs.mendix.com/refguide/reference-selector/#selectable-objects
Mendix autogenerates the possible constrain option here. In this case you can chose the path that constrains the submitters to the ones associated with the client with your contractor.
Hope this Helps!
Hey Yordan,
You can visit to this question, here I have explained how to achieve a requirement of similar condition,
https://forum.mendix.com/link/questions/119063
you can use this idea to achieve what you want.
Let me know if you face any issues.
Hope it helps!!