If you think Docker container as a virtual machine (VM) on your server then you can understand why you couldn't see your actual server's folders. This is how containers work, it isolates the resources from the host. In order to achieve your goal, you can duplicate the line under "volumes" like this:
Code:
volumes:
- /srv/dev-disk-by-label-Files/Calibre:/config
- /srv/dev-disk-by-label-Files/MyCalibreLibs:/MyLibs
Just be very careful about the line indent, it has to be exactly the same as the one above and use whitespaces only.
Here is the simple explanation of the line:
- It maps host's folder to VM's folder so you can see it from the containerized Calibre
- the left part of ":" is the one on the host, your actual server, it must exist and should contain you existing library
- the right part will be the one you look for the library when switching library in Calibre
For multiple libraries, you have two options
- put all your libraries under the same folder then map the folder to VM, or
- repeat the volume mapping line per library
Hope that helps!