Requirement: sync label changes from epic to story to sub-task.
For example, epic has label "a" and "b", story has label "b" and "c", sub-task has "d".
When: epic's label changes from "a" "b" to "a" "x", story should have "a" "x" "c" instead, and sub-task changes its label to "a" "x" "d" as well.
I know the change value of label is an array other than simply deleting "b" from epic, so considering "a" is a change to epic is also accepted to me, as long as the requirement can be fulfilled.
I tried many searches in community and happened to find a recommendation of a complex lookup function - but it's quite complex to me and the result didn't come positive.
I also a bit curious why there's no easy way to implement this automation requirement, since a label change and sync is a quite common action.