@Kristian_Sekse Thanks for sharing this new tip. Usually I need to add all members as collaborators for meeting notes, so I need that everyone has access immediately when available, that’s why I currently use the “duplicating” method I mentionned above. Nevertheless, I didn’t know it was possible to multi select tasks and then add collaborators, great to know 
Concerning the feature request, @Alexis has already created a new #productfeedback thread with the idea. You can have access here to complete the idea and vote for the idea : Add all project collaborators to a task
Julien