Follow-up to T272355
First case: Any changes made to a template invocation should cause the close box to trigger a prompt to not destroy unsaved work. The close box is displayed when editing an existing template.
Note that the "Apply changes" button already depends on something similar the logic we need. I would expect the warning and the save button to respect the same condition, actually. If we want to make this change detection fancier later, these improvements can be made to both save and cancel workflows.
Second case: Any changes made to a template within a multi-part template invocation should cause the trash can in the toolbar to trigger a prompt.
This work is currently deprioritized.