a substantive activity Even though I read the manual, I don't really know how t

To create your recurring task, select the "recurring" planning mode on your activity in the progress > management section
Then fill in the daily workload over a working week which will automatically apply to the total duration of the project on which it depends.

you find this information in our online manual or by pressing the F1 key directly from your ProjeQtOr session
Planning mode ​​​​​​​
Recurrent assignment