This is my second suggestion on the Scratch editor layout. My prior suggestion didn't receive much support, so I'm trying again.

This time, instead of being stuck with a fixed UI, my suggestion is that every single dock can be moved, resized, even duplicated or deleted. Docks can also be arranged in tabs. This allows for people to customize their workspace layout to better fit their workflow. Such a feature is already quite popular, in many game development software so I don't see why it isn't here.

P.S. No, it won't be a fixed layout. Again, this will be dynamic, so people can customize their layout to fit their workflow. The tiny preview and being unable to see the costume editor constantly are the main reasons I'm suggesting this.