Changing the input routing on instrument from “All MIDI Inputs” to “Not Connected” works, however, the change is not reflected in the GUI.
In which window? Project? MixConsole?
It was in the project window.
I will verify that I can reproduce today (I hade a decent workload yesterday). I stumbled as I needed to turn off MIDI listening for a couple of Halion tracks. I changed, but the GUI jumped back to previous setting. It seem to refresh and correct itself as another track got selected.