External Storage -> user variable in share name

Hello Nextclouders,
we would like to get our SMB/CIFS Shares to work with Nextcloud.
Problem is, every user has it’s own share. When I try to use the $user variable in the “Share” Field it does not work. Is there any chance to get this working? Workaround or something like that?

LDAP users are loggin in to Nextcloud with last_name.first_name
Share should be last_name.first_name$ ($user$)