Hey @JERI,
you mean you have all parent tasks set up already and now want to add the same set of subtasks with dependencies between them?
So you can also add subtasks to tasks via rule and the trigger could for example be a specific selection via a custom field or all tasks in added to a stage but the problem is that dependencies are not supported yet. You can vote for this feature here.
Now the other thing I was testing is to duplicate the task (with the subtasks and dependencies)
And then merge the task into the main task where you need the subtasks at. This will move the subtasks and dependencies over.
The same can be achieved by creating a new task from the task template (that has all the subtasks and dependencies set up) and then marking the task as duplicate of the other task where you need them.
I know it is not ideal but I cannot think of another solution for your case if you have 60 tasks created and each task needs subtasks with different dependencies.
I mean in list view you can bulk edit tasks and add dependencies but if all have different dependencies this is not ideal also.