I am a fan of appinventor and I would like to suggest something that I believe that's simple to add, and would increase productivity with appinventor: it's to add tabs (like we do in our browser) to organize the blocks.
When the code increases, the blocks use too many space.
With tabs, we could separate in logical parts (ie: by event -onload,onclick or by component - button1,image2,etc)
It would appear like this:
