I don't see my MIDI device in Keysight

The most common reason to not see your MIDI device in the device selection dropdown is because it is already being used in another program.

MIDI (1.x) devices are exclusive, i.e. they can only be used in one program at once. Once a program begins using the stream of MIDI events from a device, no other program can receive those events.

You will need to follow this guide on splitting the incoming MIDI event stream into multiple devices, one for each program to use.

When I bind my MIDI device in Keysight, I can't use it elsewhere!

This is the exact issue as outlined above, but where you have bound the MIDI device in Keysight first before trying to bind it in another program.

I unbound my MIDI device, and now it won't bind again!

This is an unsolved and unsolveable Keysight problem. Keysight does not properly "release" a MIDI device when unbinding from it, and continues to consume the stream of MIDI events. This is due to Keysight using the Unreal-Engine-native "black-box" experimental MIDI plugin, which does not provide nearly as much functionality as one would hope.

Your only option here is to close and re-open Keysight, unfortunately.