I have a few more suggestions.
It would be great to be able to add comments in uiflow. Microbit has this option and it's very helpful. alt text
It would be great to be able to double click on the canvas and type, at which point a list of the common blocks with that typed letter would be listed and able to be selected for use. This would allow the user to more quickly access the blocks required and to stay in the flow - no pun intended. Here is an example in grasshopper. alt text