My impression is that most editors already use this or similar optimized data structures for representing the text internally.
https://www.gnu.org/software/emacs/manual/html_node/elisp/Bu...
https://news.ycombinator.com/item?id=15199642
It's basically just two stacks of lines, where a line is an array of characters. One stack has the lines before the cursor, the other has the lines after the cursor (in reverse order).
I use emacs, but ropes are a much better way to go if you're starting from scratch.
I remember starting emacs on a VAX-750 with 4 MB main memory and 8 users in the 80s.
Even in the 90s with Suns and competitors in single user usage emacs could bring things to a halt. Especially when starting a certain messaging client (hej LysKOM).
Well, back then emacs was a resource hog like today VSCode using 8GB and swapping as someone wrote here. (I would not touch VSCode with a stick). Times have changed, but emacs rather little. So today it can nearly be considered lightweight and efficient.