/var/lib/samba/usershares
But note that it is just simple file sharing if you need directory mask, create mask etc... you still need to edit the smb.conf file to create your share.
Here is an example file:
comment=
usershare_acl=S-1-1-0:R,S-1-22-1-1000:F
guest_ok=y
sharename=BabyPhotos
debian, ubuntu, mint, samba, config, var, lib, usershares, directory, etc, edit, smb, conf, usershare_acl, guest_ok, sharename, babyphotos,