I believe to rename the share all you have to do is change the label on the sdcard. (interanal share/mount mount point) power and reboot.
or
external share name is in /etc/config/samba which is (option name ‘sambashare’) and that and the 3 other settings options in that file will overwrite and replace what is actually finally used in /etc/samba/smb.conf
this was also a good read for me