You may wish to copy Pieces from a Project to your personal Library, in order to have a local backup, make edits that you do not wish to share, etc.
To do so, click on “Edit” in the top-right corner of a Project, select your Pieces using the blue checkboxes on the left, click on the black circle and click on “Copy to my library”. You will be presented with the option to also add the Pieces to one or several Setlist(s).
Note: Pieces copied from a Project into your Library will be independent copies of the Pieces contained in the Project.