I’m looking at MIDIHUb.
In the Editor, I see category of usb as though usb connection can be routed.
MIDIHub itself of course has only the one usb jack. Is there another ready or in the works to allow switching an other control for usb? That would be very useful for me. Thank you.
Hi, see this related topic: Multiple USB midi Controllers
USB MIDI controllers can be used with Midihub, if you have some USB host that can forward the USB MIDI data to and from Midihub between other USB devices. The smallest portable option would be to use a Raspberry Pi for such duties. 
Let me rephrase my question.
In the MidiHub Editor, what do the icons labeled as usb under INPUTS and OUTPUTS do?
Thanks!
The device Midihub is attached to sees Midihub as providing 4 bidirectional USB MIDI ports. The different letters correspond to different ports. They appear differently depending on the OS you’re running, see this page for what to expect.
Here’s for example how Midihub appears to Ableton on Windows:
The A, B, C, D would map to the 4 ports in sequence for both Input and Output.
I see. Thank you
