>For sure, it is a neat experiment to create something like this, but time and time again, people always resort back to tools like Sketch
The difference this time around is that the visual designer language...is the real development language.
I've also tried using these visual designers before. They all seemed half assed and had glaring limitations.
This one may end up being no exception. But I think, combined with Flutter, there may be something gold here. The key being that this visual editor is really a glorified text editor rather than a glorified art program. Sketch, for example, outputs PNGs at the end of the day. You can't throw those into your app and call it production ready. This "widget maker" outputs dart files. That's real, executable code. If the overhead visual designer is flexible enough, the only walls you may end up hitting are the ones set up by the widget implementations themselves. At that point you'd have to deal with those walls manually anyways, so you haven't lost any time really.
One of my fever dreams over the summer was to build a voice controlled Flutter widget builder, such that I could sit in front of my TV and simply transcribe a UI from my head directly into the emulator. OP's project is a good first step towards that goal. Just imagine:
"Give me a scaffold with a column layout..."
"Add a raised button to this container's body"
"Set its color to sky blue"
"Show me this widget's properties"
"Make this a stateless widget called SpecialButtonBar and have it take three arguments..."
Again, it doesn't have to do all of it. But having written code to play with is a much better starting point than having nothing. Flutter's composability means that there aren't many different approaches you or a machine can take to arrive at the same result - you will end up with very similar widget trees which means this is a task ripe for automation.