I believe you could add the "hidden" activities later,
And then using the Course Completion-Bulk Edit activity Completion option, add them to the course completion requirements.
You would need to test this, on a copy of your course.
Select the Bulk Edit activity Completion tab.
Select only the newly added activities.
Select the Edit button.
Return to the home tab for Course Completion.
The Activity Report should now have the new activities as a required value, displayed with the date you added the activity.
kind Regards
And then using the Course Completion-Bulk Edit activity Completion option, add them to the course completion requirements.
You would need to test this, on a copy of your course.
Select the Bulk Edit activity Completion tab.
Select only the newly added activities.
Select the Edit button.
Return to the home tab for Course Completion.
The Activity Report should now have the new activities as a required value, displayed with the date you added the activity.
kind Regards