Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi Max,
Thanks for taking your time and providing brief explanation about your requirement.
After reading your explanation part, I totally understand that your looking for to lock the Plan in the Planner to prevent it from editing and make the members added to that Plan can copy the tasks. Simply making the plan as template and creating a new plan with this template.
Currently Planner is having the features to Copy a Plan but Planner is limited to lock a Plan from editing and we understand how importance this feature to your scenario, apologies about the limitation. Given situation, please add your idea in Planner UserVoice.
Hope you understand and appreciate your patience.
Best Regards,
Chitrahaas