The ^ signs in the configurator only shows the occupied pins for configuration convenience, and this does not affect how the switch works.
The plugin receives a position from the switch anyway.
Eventually these ^^ will appear in all switches when the cfg file is uploaded to the configurator later..
As you've seen when testing it as direct connection it works fine, so then it should work with MUX (I assure you).
What about other switches on the MUX, are they working?