In the systemApp.js, around line 500, the source list is populated in an array. If you change the order, it will show the sources in that order.
From line 499 to line 511 in this image you can see the list of audio sources.
Rearrange them carefully and they will show up in the order that you have them arranged. Make sure that all the lines end with a comma EXCEPT the last one in the list. (Refer to original image link below).
Original Image Here: ivcmh7ppmekg9.jpg