Allow a certain transition in Epic's workflow to be executed, only if all its tasks are unresolved and have a due date set.
Add theĀ Logical validator to the desired workflow transition.
Add the following expression:
count(filterByPredicate(linkedIssues("is Epic of"), ^%{00028} != null OR ^{00012} = null)) = 0
Logical validator
count()
filterByPredicate()
linkedIssues()