Active Directory Integration and winbind default domain

I’ve succesfully installed Rockstor on a virtual machine.

I’ve found that I cannot enable the option

“winbind use default domain = true”

Though I set that option in the Samba settings, the Rockstor AD settings have the same configuration set to default and it seems Samba takes the last option as the valid one.
Can we enable some option to add configuration settings in the AD Section and keep only one parameter as valid?
Is there any other option I can use? (I’m using it to enable ssh login using AD user without domain, since it does not works so far)