I really like the simple and clean interface of Syncthing!
Since current speed and bytes left are already here it would be great to use them to calculate an ETA for download/upload of each folder and also show the time left for the sync status of each device. After successful transfers this line is hidden.
Another helpful information would be to see the total remaining size (sum of all remaining transfers) of all connected folder for each device. Also displaying speed in KB/s, MB/s is more intuitive.