PRP_53,
the instructions on the link you sent is temporary. it did react to the adding of folders or files. it accepted a current folder that used to be in my wallpaper's library - then the other folders (i have added over time) popped back into view.
but this only lasted for about 6 days. it has gone back to the error message and once again will not accept any folder i try to add.
i am kinda back where i started with this. i was hoping this was a system-wide problem that the software writers could correct via an update, but there are not enough squeaky wheels to be heard. let me know what we can do next.
btw - this is what i sent to the survey that asked me if your solution helped - i said no, because:
"...this answer/reply is just the standard way of adding folders and files, aka photographs.
i keep getting the error message "...Settings Error The operation couldn't be completed. com.apple.extensionKit.errorDomainerror15.)..."
PRP_53 was helpful+!..."
thanks again again