Just wanted to make the suggestion that you move the [+] button to the end of a field’s contents or make it an overlay, rather than have it at the beginning. This is because when you make a field active the [+] button appears and shifts all the existing content to the right. But, if you were aiming to click on and access the existing content in the first place, it’s no longer where it used to be and the second click on the double click misses the mark. If you have relatively small field widths due to the screen size this can be very irritating indeed. Having the button appear at the end or as an overlay would solve that problem, as the content wouldn’t shift unexpectedly.
All the best,