It's currently impossible to create an unlimited filter in a role if the user is in any organization/location scope. The user needs to be in 'any organization/any location' to be able to do it.

It might make sense to not allow users to create unlimited filters in this situation but the current behavior is that so the user creates the filter, the 'unlimited' field gets fixed without the user knowing, and it's a bit confusing. Maybe disabling the field would be a sensible choice.