@Mats-0 so you mount that shared folder on your mm system in some location. typically those end up in the /media/username folder

then you use the ln command to create a linked directory to that folder

in the MMM-ImagesPhotos folder, rename the upload folder out out the way

mv upload upload-old

then create the linked upload

sudo ln -s the-mounted-path upload

I add a line to my /etc/fstab to create the link to my server share at boot time.

I have never seen a Synology mas, so I don’t know how you get those volumes mounted on the consuming systems are they using windows
samba shares?