Problem: customers want to be able to bulk create subtasks.
Issue: no way to do this in current system.
Possible approaches (in order of preference):
1. Jelly tag to create subtasks, either as a sub tag of the parent create or as a stand-alone tag.
2. Jelly tag to associate a subitem to an existing item.
3. Allow bulk change of task to subtask. This would then allow a cludge of creating the items as a false issue type (foo), then changing all items of type foo to subitems of a particular parent item. Though there might be hope here in 3.9, but was denied.