Originally Posted by Cirrus550
Unofficially you could try to play around with windows symbolic directory links. I have succesfully used them in similar situations. I have not used them in years so details are bit fuzzy.
Maybe this sheds some light to the subject if you are interested in tinkering: https://www.2brightsparks.com/resources/articles/ntfs-hard-links-junctions-and-symbolic-links.html
This. Reparse points / junctions / mounted folders is the way to go.

In addition to the article referenced by Cirrus550, you can also look here, to pick up a bit of terminology: https://en.wikipedia.org/wiki/NTFS_reparse_point . Another pretty good description of what they are: https://superuser.com/questions/1297273/what-is-a-reparse-point-and-why-is-it-named-so . Or you can just google it yourself.

NB: Make sure you know what you are doing. Careless playing with your file system on this level can screw up your drive(s) big time.