I'm using Favourites to list the series currently being watched (right now: Robin's Nest, The Saint, Only Fools and Horses, Homeland). Itis doing what I want and I thought I'd change "Favourites" to "Watching". No problem with Home.xml but strings.po in the skin (eg "Add to Favourites") is giving me trouble. I can edit strings.po with Notepad++ but a) I end up with a much larger file (16kb -> 553 kb) and b) it doesn't work.
It seems to work if I edit strings.po in the Kodi system rather than the skin. I don't want to do this because of implications for upgrading.