I'm a little bit wary about this flag change because of the problem before with multiple manual trigger submission, which was fixed by putting in the `manual_trigger = False` later along the process in task.py (see [here](https://github.com/cylc/cylc/blob/6f9da292474e0eec1db482571a6c4f0af5230966/lib/cylc/task_types/task.py#L290-L292) and [here](https://github.com/cylc/cylc/blob/6f9da292474e0eec1db482571a6c4f0af5230966/lib/cylc/task_types/task.py#L404)).

I'll do some testing and make sure this doesn't resurrect.