Most tabs on the Project Default Layout are controlled by security access rights.
But did you know that in Clarity v13 you can actually override the security access by permanently hiding tabs on the page layout?
In the configuration of the page layout you can 'deactivate' a tab. This means that it will never appear on the page layout regardless of the security access rights granted to the user.
This may be useful for creating your own copy of the project default page layout and deactivating different tabs for use in different types of projects. When the tab is active, it will use the built-in security access rights for visibility.
For an example of how this works, refer to the following Technical Article:
TEC442078 : Clarity: How do I hide the 'Financial Plan', 'Hierarchy' or 'Processes' tab on the Project object