The first thing that comes to mind is using a symlink. Find the folder path of your nas pictures on your machine and save that for later. Then open your home folder in a terminal. Since your home folder shows in the image editor, that tells me you could create a symlink there and the image editor would see it.
cd ~/
#Change your nasfolder path to the actual path
ln -s /your/nasfolder /home/hans-de-ruiter/Pictures/nasPictures
This will not duplicate the files, just create a logical pointer or “shortcut” to where your NAS stuff actually is.