@Patrick_EMIN I am not aware of any feature in Asana to do this but there may be some other resources to look at.
- Check with @Phil_Seeman and his integration to see if he can be of any help.
- Consider a CSV Import of the task and subtasks. CSV + Asana: Import work data into Asana • Asana
- If you do a CSV import you can write your logic in Excel to accomplish what you need. I posted an example of this some time ago. Import With Dynamic Due Dates