How can I "store relative pathnames" in ArcGIS Pro?

[SabineSchnichels]

Are absolute pathnames the default option? Does ArcGIS Pro always store absolute pathnames or is there a possibility to change this to relative?

[LindsayRaabe_FPCWA]

I've just added an extra "Solution" to the post which simplifies the findings down to a couple of clear 1 liners. It isn't a solution to how to use Absolute paths all the time, but it does clearly explain the behaviour around 'moving' projects and what happens to the relative pathways. 

For what it's worth, we manage a lot of ArcGIS Pro project templates, stored on a G drive. Our users have been instructed to Open and Save As these to their desired location so that all pathways are maintained. If they were to Copy/Paste the project instead, all the pathways mapped to a Drive letter would be updated (relative pathways). I'm about to do some more testing on UNC pathways - I've seen text stating that these don't change, which may be an (annoying) solution for us. All our GIS data is stored on network Drives (G & V) or in ArcGIS Online as a feature service (no issues there at least).