Library variable sets make it possible to share variables between projects. You can create them from the Variable Sets tab in the Library area, by clicking Add new variable set.
Just like defining project variables, library variables can be scoped to environments, machines or roles.
Once library variable sets have been defined, they can be referenced from a project by viewing the project variables, selecting Library Sets and clicking Include library variable sets.
Select the variable set to include and click the Save button.
The Project Variables page, while under Library Sets will show the shared variable set that has been included.