Plans - Expressions - custome attributes not all showing

I want to be able to set plan filter to be specific on a given custom attribute, so breakdown the list of the items in the plan view.

On Phase Plan of formal Project template, custom attribute field not showing on Filter > expression list.

Have added to Plan attributes > Plan Mapping, this now appears in the expression list but does not actually do the filter or the ! exclude.

Have I missed any other changes that need to de done on the process