This partition is dedicated for storing data shared by multiple OSes, should one be installed here. It is formatted in exFAT, as it is the simplest yet advanced filesystem that Windows supports, and also the only one that has open specs, therefore having the most potential support. Links or other similar filesystem feature should be used to redirect their own user folders here.
The aim of creating this partition is to increase integration between OSes, in a partition everyone can read and (hopefully) never fails.
What belongs here:
Files that are OS-agnostic, that is they do not care where they are opened or created at.
These files include documents, images, audios, videos, project files, etc.
External assets that could be characterized as such may also be stored here.
What DOESN'T belong here:
Programs that must run natively, or by usage of some compatibility layer (such as Wine or WSL).
This doesn't apply to programs that must be run by some other architecture absent in this laptop, whether it be a physical one that's emulated or interpreted by a virtual machine.
Programs built by some source code here are exempt to this rule, as long as they aren't stored elsewhere in this partition.
Files and folders relevant to one OS but not to others, except those that the OS requires.