It is now possible to create a subgroup directly from the draft of an event, but this is a possibility that coaches have called for.

You can select one of these categories - all, attending, no answer, not attending and then click on the three dots on the right and select "Create subgroup".

Then the window opens where subgroups are created with pre-filled members who were on the list, e.g. if the coach selects the "Attendance" list, everyone who is registered for the event will join that sub-group.