This filter is used to add flexibility to the page title. By default, the filter should provide a string that has an argument that is used as a placeholder for the actual page title. Here is how the string looks like :

__( '%s — NexoPOS 4' );

This can obviously be changed using the filter "ns-page-title" like that.

Note that these modifications should be performed on the module service provider, especially on the "register" method.