This for JIRA Cloud

We use JIRA Portfolio's Parent Link field to link JIRA epics (SAFe Features) up to SAFe Epics (custom issue type). 

I need to be able to identify all issues based on their grandparent, and ideally on any other attribute of the JIRA Epic they belong to.

Either live in JQL as sub-queries, or some mechanism to (regularly or on request) to find them and label them so they can be found via that label search.

For example, I want to be able to have a board that showed all issues that were part of any epic whose Parent Link was a specific issue (SAFe Epic)... something like:

{{ "Epic Link" in ("Parent Link" = ABC-53)}}

This of course fails.

I've tried in Cloud using post-function based approaches (standard and JMWE), and have explored most of the add-ons available in cloud, but can't figure out how to do this.

This is fundamental in our SAFe adoption so we can show all the work supporting a particular SAFe Epic (which may be split across multiple Features in several release trains / programs, and across multiple teams). 

Please advise when some workaround of capability will be available in Cloud, or if this can be achieved through a cloud add-on or other approach.