I think this should be added as an option disabled by default, exactly as it is done in Draw Letters and Draw Numbers, to not disrupt workflow of people who use it just to train mouse usage/motor coordination and may not like to have to press a button to go to next level.

Also this can be added to the 3 activities erase, erase_clic and erase_2clic.

Okay, sure.

https://invent.kde.org/education/gcompris/-/merge_requests/58