I realized too late that _ is used for i18n. Well, 10 minutes late maybe, but I had already completed the first test GUI and it looked so nice that I could not turn back :) If you have ideas for an alternative syntax, I am all ears.
If you look in the tutorial, there is also a ___ (three underscores) magic widget for special layouts :) I can see the difference between one and three, but between two and three it becomes difficult :)