List all issues, from multiple projects, linked to multiple epics from 1 project.

Question

Greetings,
I have one Project, "ProjectMain" where I create "CrossFunctional" Epics (Issues created in, "Project1", "Project2"... linked to Epic in ProjectMain). 
In "ProjectMain" I would like a filter that can show me all issues from other Projects linked to all epics in "ProjectMain"

I had a filter that works, but only when I prioritise the Epics in ProjectMain, and prioritise the issues linked to them. 
I am looking for a workaround so I do not require to prioritise (people forget).

Current solution:

project in (ProjectMain, Project1, Project2...) AND issuetype in (Epic, "External Story", Feature, Story) AND priority = Highest ORDER BY Rank ASC

I am trying to create a more dynamic query where I can use this filter:

ProjectMain-ActiveEpics:  project = ProjectMain AND issuetype = Epic ORDER BY Rank ASC

Can I get a list of all issues in Project1, Project2 linked to Epics in ProjectMain using the named filter above, ProjectMain-ActiveEpics.

I have tried all kinds of .... IN (Filter = "ProjectMain-ActiveEpics") but...

Any help will be appreciated.

Andy Kelly_w1muct · Answer

Thanks for that. I have been looking at plugins, but, for now, would rather work around them.

Fran Garcia · Answer

with scriptrunner it would be something like

issuefunction in issuesInEpics("project=ProjectMain" and status != closed) and project in (Project1, Project2)

Without any plugin it doesn't sound easy