Charles_Gibbs:
I do have to exit the the MPPT window first so that the Victron software can pick up the BMV once that happens I can click on the BMV Icon and then view its data.Your interpretation is 100% correct!
The piece in blue suggests to me that the piece in green is not entirely correct.
I asked if the Victron software would recognize the changed data, but you are saying that it does not unless you do something with the Victron software. That sort of attention to detail is essential when dealing with computer programs.
If you want to feed two serial inputs into the Arduino and use it to take the place of the DPDT switch then you will also need to co-ordinate that change with whatever actions you need to do with the Victron software. For example maybe you need to close the MPPT window before telling the Arduino to switch to listening for the BMV.
...R