Ideally you need a block based editor. Kate is the only modern editor that I’ve used that I know has a block mode. Any others?
Now the question is how do you get a block based editor on a webpage?
Now the question is how do you get a block based editor on a webpage?
They're so useful, everyone should know them anyway: Need a column of '//' rather than '/* <long_comment_block> */', or vice-versa?. One click-drag and 4-5 keystrokes will do it.
Depending on how you define "modern", vim (and I assume neo-vim) support block-mode.