In order to save a project under a new name,
select the entry
Project / Save
as from the context menu of the project. You can enter the
new project name in the following dialog.
If you want to use an already existing name, you will receive an according message.
With this functionality e.g. it is possible to create a copy of the existing project, which the can be edited independently.
For this Project A is copied with Save as from the context menu and then can be edited. Then it is saved and Project B (again contect menu - Save as).
Depending on how much the two projects differ, this can save mor time than exportint/importing project parts.