Charles_Gibbs:
It's the standard Victron connect app, running on windows.
I have no idea what "the standard Victron app" is - I did not even know such thing existed before you mentioned it.
What I want to do is connect both the victron devices to the arduino, and the arduino to the usb on my laptop and then select the devices one at a time and then read what is being sent through via the victron app as it is, I would like to be able to use the arduino as a two input ONE read at a time device but be able to switch between the two via the app.
Your way of describing things is very imprecise. For example you talk about victron devices and victron app without clearly stating what each of them is so it is very hard to understand.
My wild guess is that the Victron program is designed to detect multiple USB connections and can either select between them or show data from both of them.
If so there is no possibility (short of re-writing the Victron program) of getting it to think that one Arduino is two different things because all it will see is one USB connection.
As I mentioned earlier you either need access to the documentation for the Victron programming interface or you need to ignore the Victron program completely and just write your own PC program.
...R
PS... please don't post pictures of text (as in your 3rd image). It is quite unreadable. Just copy and paste text.