The answer to ganging several lock-and-cancel valves together to get an
"all registers off" function is to put a check valve in line with each
off pouch.  The normally open side of the check valve goes toward the
pouch.  The normally closed sides are teed together and tubed to the
tracker "all off" slot.  All bleeds are left in place.

I made the lock-and-cancels and the check valves from Doyle Lane valves.
They work great.

Fritz Gellerman