You can currently set all of the paths for linked files in your scene globally from the File > External Data menu.

However there are certain use cases for having mixed pathing in your file.

Proposal:

• Add Make Path Absolute and Make Path Relative to the right click menu of all file path fields.

I have written a simple script that converts Relative Paths to Absolute Paths here if any developers are interested in adding this to branch.

Code on Github

github.com/admorris86/Blender-Scripts/blob/main/Convert_RelativePath_toAbsPath.py