I’m facing the same issue with this post: Solved: Workflow: Display message to close all sub-tasks i...
I have Sub-Task Blocking Condition set to prevent closing a parent issue when any of the sub-tasks are not closed. It successfully hides the transition status, however it does not give the user any indication as to why they can’t close the ticket.
But is there any alternative besides Script runner and JMWE, I mean not using other app?