hi John,
i'm almost always in the situation where QJackCtl doesn't see all the interfaces on my machine because i have lots of them. a gaggle of monitors, each with an audio interface. a couple of hardware interfaces. a flock of virtual devices (mostly Loopback).
my workaround is to remove devices until the one i'm after shows up in QJackCtl (restarting QJackCtl each time so it can reregister the list). i select the target device, save that configuration in QJackCtl and then add all the extra devices back in. in my case all i usually have to do is turn off all Loopback devices except the one i want QJackCtl to use -- my target device shows up, i select/save it and turn the rest back on.