I fixed it!
Situation: I had moved my pics folder to my D:drive, where I want it to reside, along with other data folders & files, safely separate from my system drive C:, in case of a system crash. Folder D:\Pictures did not show in the Pictures Library nor did it display a Location tab. Also, the Pictures Library did not contain any folder.
With utility program EnhanceMySe7en I ran option "System Repair"(= Repair All System Components). I expected the operation to last quite some time, similar to SFC Scannow, but it took merely abt 2 minutes.:)
After this, as there still was no C:\Users\username\Pictures folder, I created that (empty) folder. Looking at this new Pictures folder's properties, the earlier missing Location tab now showed up.
It was now easy in the Locations tab to "move" this new empty Pictures folder to D:\Pictures, that contains my picture files. Now the Pictures Library points to D:\Pictures, as it's supposed to do.:)
Maybe my explanation is not very clear, and not sure if all described steps were really necessary, but it works now, and I consider my problem solved. I can now enjoy my purist system.
(until further notice
)
Cheers Uffe