This is pretty slick. Now that I’m back on nvALT, I needed to figure this out.
You can drag an entire folder to the Marked icon and it will open a window which always shows the most recently edited text file in the folder. Marked watches for changes in all files, then looks for the newest text file and displays it. If the file is the same as the last check, then it scrolls to the edit position and works as usual.