Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi Matt,
Based on your description, I assume you are referring to the following article:
If you want to remove the link between your Project Tasks & Planner, you could simply click on the Remove link in the Project Desktop application.
If you what you mean is the plan is still appearing under Planner Hub even if you deleted it. Please go to Office 365 Admin Center > Group, find the Office 365 Group which is related with your Plan, then delete that group, the Plan should be deleted automatically with it.
Please keep us posted, if there is any misunderstanding on your question, feel free to point out.
Regards,
Alex Chen