Do you need to only connect one to your computer so as to be sure which you’re editing?
[It may be possible in linux to open more than one instance of Editor, but doesn’t seem so in Mac OsX]
Similarly, do the 4 USB port names then get ambiguous, making it only viable to connect to the 2nd via MIDI DIN (or have a separate host like an rPi to send messages via USB)?
Hey, macOS seems to be designed to prefer single instances of applications indeed, but it’s possible to get around that by launching additional instances of the program using this command executed in a terminal:
open -n /Applications/Midihub\ Editor.app/Contents/MacOS/Midihub\ Editor
What will happen when there’s more than one device attached at a time - when you click Connect, the editor will open a list of all the available devices, the information displayed will also include the unique Serial Number of each device. You can pick which device to connect to from the list. Then you can launch the second instance of the editor, click Connect, it would show the list again, or if there’s only a single device without an active connection, it would just connect to it immediately.
The Editor instances can be differentiated from one another based on the Serial Number displayed at the bottom right.
That said, I did just give this a try on macOS, but there’s a bug - the 2nd instance of the editor interferes with the first instance’s connection and gets it disconnected. We’ll get that fixed. 
Thanks for the tip.
My 2nd hub hasn’t yet arrived so didn’t get to the bug!
Onto the 2nd question. IF you can have two instances running, do apps (or modules like python.mido) get to see 8 usb ports?
Yes, the apps will see more ports, the names should include the serial numbers too. Windows is known to sometimes mix the devices up and show wrong names, to workaround that, we can provide custom firmware builds with changed USB product ids, so Windows has less trouble keeping track of what’s what.
So, even if I can’t get both devices Editable just right now, I can have them both accessible to say MIDI Patchbay and send messages between?
Excellent!
Yes, that should work
Glad I took a punt on Midihub the Sequel, then.
(Hard to get here in the UK, particularly since our decision to leave the EU )
Now I can have a dedicated Mapping* hub… 
(*until your hinted updates make that less in need of cunning plans 
)
Yep, now seems fixed.
I’ll give a proper test in next couple of days: 2 MIDI monitors side-by-side!
