You have 2 options:
 Install a PPA "fix" so that you can continue to do this through caja.
The details are listed in the bug report: https://bugs.launchpad.net/ubuntu/+source/samba/+bug/1872476
And the PPA can be found here: https://launchpad.net/~sergiodj/+archive/ubuntu/samba-bug1872476-v2
 I would strongly suggest you use a CIFS mount instead.
This way you can leave smb.conf alone and create a specific mount to your NAS box with earlier versions of smb.
There's an example of how to do that in another question here: 20.04 upgrade makes NAS unavailble
EDIT: I understand your reluctance to have mounts in fstab but it could be set up as a systemd automount then it doesn't mount on boot - it will only mount when you access the mount point.
The following is just a suggestion. If Step  doesn't work there is no point in setting it up in fstab.
 Do a temporary mount first to make sure it works:
** Create a mount point ( do not put it in your home directory or under /media:
sudo mkdir /mnt/NASx
** Do a temporary mount:
sudo mount -t cifs //nas-ip-address/share-name /mnt/NASx -o username=xxxx,password=yyyy,uid=1000,vers=1.0,sec=ntlm
 If step  works you can set this up as an automount in fstab:
** Unmount the share:
sudo umount /mnt/NASx
** Add this to /etc/fstab
//nas-ip-address/share-name /mnt/NASx cifs username=xxxx,password=yyyy,uid=1000,vers=1.0,sec=ntlm,noauto,x-systemd.automount 0 0
** THen reset systemd:
sudo systemctl daemon-reload
sudo systemctl restart remote-fs.target
** Then access /mnt/NASx to verify its contents.
noauto = prevents the mounting at boot.
x-systemd.automount = mount the remote share only when the mount point is accessed.