And, good demo, I like it.
The Part 1 demo that you might be looking at is actually the original JavaScript app from two years ago. However, the Pascal to JavaScript version from Part 4 is visually and functionally identical so I didn't post it.
Remember, Part 4 is the only new content here.
Ok. I see that Lazarus can open JS files..
And, well, is the way It's better to design UI, In my opinion. Like in your demo, with Code.
In the FPC Paymo Widget I made, I still can't figure on how to solve the High DPI thing on Windows, designed with the Forms editor, but the elements I create by code are always perfectly aligned and sized.
Modern languages like Dart are doing like this, for example for Fuchsia OS (Also Android / iOS), UI made with Flutter are coded like that also, there is no WYSWYG.