There is contenteditable and EditContext hese days, it's not that hard to make a simple WYSIWYG editor. An LLM could figure out how to operationalize these things quicker than I could.

To be clear, I'm not talking about a rich-text editor. I'm talking about a notion-like interface where you can drag and drop different types of elements to a canvas to build rich content, and adjust the blocks horizontally or vertically via drag and drop.