If you want to edit Scheduled Issue Sub-Task, navigate to a Scheduled Issue details page (visible only after accessing particular issue) and choose Edit icon (1) next to the Sub-Task:
The
following screen will appear after After clicking the pencil icon:
After completing the edition please click "Save" to finalize this procedure(edit) icon, fill in all needed fields of an opened sub-task of scheduled issue and press "Save" button at the bottom of the page to keep changes.