I did contact support. They say it is not controllable from the interface. It needs to be. If you have a second router (used as a bridge), it also wants to control WINS. So do the Windows and Macs! They fight to be the master browser, and that kills the displayed samba shares.
Please put this in as an urgent request. At the very least, you need to be able to control its number (0-100). The highest one wins the fight.