Card design showing flagged "child issues"

[María Luaces]

I would like the cards of a kanban board at the epic level, to make a differentiation between epics that have user stories flagged and epics that don't use the card design section in the board configuration (for example with a colour).

Is it possible to do it through a JQL query? I can't use "flagged is not EMPTY", because I want it to reference the items linked to the card item, not the card item itself. It's a board just to visualize Epics in this case.

Thanks