I create a N:1 relationship between product entity and contact entity, there is a subgrid of product on the contact form. I set the Default View of subgrid to a custom view, and set the View Selector to off. This subgrid only display the products of the custom view, which is correct.

However, when I add the existing products, I can select all the view, not just the custom view I set, so I can add all the products. If I add a product that is not in the custom view, there is no reminder message, nothing happened.

This is the problem. If the user doesn't know that the subgrid is restricted to the view, then they can't correctly add records to the subgrid because there are no hints if a non-compliant record is added to the subgrid.

Or, when adding records into the subgrid, in the lookup records form, the selection range of the view should not be all views, only the views of the subnets that are set. In my case, it should only be a custom view of the product entity.