I just came here to share this too 🙂 Really nice to see someone trying different angles on structure editing...

I like it. Here’s how I would develop it further: 1. Large expressions are automatically wrapped (at token/tile boundaries) across multiple lines, to fit the amount of horizontal space in the window. Like word wrapping in a word processor. 2. You can select and copy an expression fragment as text into the clipboard. Or paste text from the clipboard. 3. Whatever text gets copied into the clipboard, you can type that text verbatim on the keyboard to reproduce the expression in the tylr UI. So you can explicitly type the ‘)’ character that ends a parenthesized subexpression, for example, instead of pressing the right-arrow key to skip over the ‘)’ that was inserted for you.