We created a custom form to add fields into our Change tickets. We use the fields defined therein to sort tickets for review during our weekly Change Enablement meetings.
With the Change Catalog release and the ability to create Change Ticket templates, I jumped on that so that it is easier to create Log Only, Standard, Emergency, or Constraint Change type tickets. The custom form was being applied and the process fields were being used, I thought due to them being mandatory - which they never were due to the way Custom Forms work in allowing sorting but not being able to be mandatory unless changes are Ad-hoc, which I did not and do not want.
Recently, my folks stopped inputting data into that field making it difficult to sort or prioritize Production area tickets versus Support area tickets for review (Production first in case of emergency on the floor). So I explicitly defined those fields in each change template. Naturally, those process fields are unable to be filtered by in the portal view.
I think it would be advantageous no matter if you are looking at Incidents or Changes to be able to sort by those various process fields we each define instead of having to export that data in order to sort.