For an alternative that is "less intrusive", i.e. doesn't involve editing FolderDescriptions or affect the shell namespace, see the alternative answer I recently added to this question: https://superuser.com/a/1768074/881098 . It adds an item to the background context menu of file folders that will navigate to the file system location for folders displaying namespace paths in the Address Bar such as:
<Full User Name> (shell:UsersFilesFolder)
This PC\Documents
to (aasuming defaults for example only):
This PC\Windows (C:)\Users\<UserProfileFolder>
This PC\Windows (C:)\Users\<UserProfileFolder>\Documents
...and now back to the original answer...
Not sure if this will have unintended side-effects, but experimenting with the Pictures folder, I deleted the current Quick Access pin, then in the registry, deleted the 'ParsingName' value under:
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{0ddd015d-b06c-45d5-8c4c-f59713854639}
and
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions\{33E28130-4E1E-4676-835A-98395C3BC3BB}
Restarted, navigated to C:\Users\Keith and pinned Pictures to Quick Access. the result was the Address Bar now showed Pictures path as a subfolder of the UserProfile folder rooted in the Desktop:

So then I delected the ParsingName under {f3ce0f7c-4901-4acc-8648-d5d44b04ef8f} (UsersFilesFolder) and that produced the desired result (after restarting Explorer):

Back up HKLM\...\FolderDescriptions before testing.