I use colors to differentiate files which works well for me. Once the selected file is opened, the line for that file turns gray. Granted this is a unique color but when one uses multiple programs that’s not always so obvious. The other change that the existing program uses is to ‘square off’ the left edge of the selected line. This is good but I think it could be better. I’ve attached a screen shot to show the problem. The arrows show the complete line of gray, ‘squared off’ instead of rounded and the second arrow shows the color ‘blip’ also added to selected line. It helps but I still find myself having to search to find the right file.