Under the hood, the system actually translates fstab for systemd, so there is also sense in making the configuration directly for it.
Now a few tricks:
Once a partition is mounted, you can access it through its mount folder. But if you want “direct link” in your file manager side-panel, you can either:
– use a folder in /media as mount point
– add x-gvfs-show as mount option
You can easily check if your automount configuration works without rebooting : mount -a
Lastly, a question :
Why are you trying to mount your extra partition as the root folder?