Hi:
We don't have a delete features for locations at this time. Plan only uses a single location set - the one that you set as the default. The other location sets will not be visible to users outside of the Project Admin/Locations page.
It's important to be careful when you are changing location sets. If you've already used an existing location set to assign locations to activities, changing to a different location set will remove the location assignments from those locations. If you have questions about how to set up your locations, please contact Autodesk support.
mike.d
Head of BIM 360 Product Management & UX