You can drag and drop files and/or folders from the virtual disk to DEVONthink in order to import or just reference (aka „index“) them.

For indexed files/folders, DEVONthink automatically updates them when changes/additions occur via Papers (though this probably requires re-selecting them in DEVONthink).

If you unmount the virtual disk, DEVONthink will complain, but it will display the files again when the virtual disk is available again.

See this article for further information about the virtual file system.