If you want File Manager to show your mounted directory, you have to mount it to a folder under /home/user/MyDocs/ (or mount it as a dir on one of the SD cards), so for me, I have a folder called /home/user/MyDocs/lan that has a subfolder for each of my SMB mounts.

If you could get to the shared folder via the file manager before, you probably don't need my instructions. They are only for people who couldn't access the share before due to a password or other problems.

I also found that the standard umount works fine, I didn't need umount.cifs.