In harvest 5.x and 7.x, the path is NOT versioned, and path is global. That is why you can update the baseline of a project when a repository is updated.
Starting in Harvest R12.x with refactoring change, the item path is now versioned. So once a repository is baselined, all the paths are versioned, you can not use admin to add or remove paths anymore.
To add a new path after the project has been baselined you will need to use the Create Path process.