How to filter on Epics and custom fields, for Portfolio

[Roald]

I'm about to give up on this but want to try here before I throw in the towel.

I have the following setup:

1. Jira Cloud with Portfolio
2. One project, multiple teams
3. Custom workflow with several Kanban boards covering stages from roadmap to deployment
4. Team Kanban boards for the dev/sprint part
5. Initiatives (used for roadmap priority segmentation), Epics, Stories, Subtask hierarchy
6. We plan on Epic level (currently)

This setup somewhat works with Portfolio (apart from all sorts of Portfolio issues that I won't even go into here). In the source definition of Portfolio I select all relevant Epics per Initiative I want to include in the plan, allowing me to add lower priority epics to 'fill up' capacity.

As I may need to rename Epic to Features soon (currently splitting epics into multiple epics to mimic features, for more detailed planning) I need to make the Initiatives level free to act as Epics. I therefore created two custom fields for epic level issues, one for roadmap priority and one for scope inclusion/exclusion field. Selecting on those fields I should be able to find all Epics with priority 1 AND all other priorities that have been explicitly included. I do NOT want to set priority and scope fields on all involved issues unless it can be done automatically when setting the epic fields.

And now the tricky bit: I need a filter that will select for Portfolio source:

1. All epics with priority field set to a specific value or values OR scope field set to included
2. All user stories related to the epics identified in step 1 (not any other issuetype)

And a few limitations:

1. Any sort of pricey (meaning any cost above zero) plugin is not an option right now
2. Using hardcoded issuekeys is not an option
3. In the new situation (initatives turned epics, epics turned features and planning on feature level) the adapted filter should still work

Any ideas?