In a network firewall rule, create a new FQDN destination (example.mytest.local) while configuring the FQDN create a new FQDN group mytest and save, returning to firewall rule.
Try to add the new FQDN Group mytest to the firewall rule as a destination and it won't be visible.
If you exit or save the firewall rule and open it back up, it will be available to add as a destination.