In case anyone hasn't seen it this CppCon talk https://youtu.be/sPhpelUfu8Q talks about rrb-trees and how they're a great data structure for writing a text editor that can handle unlimited sized documents without locking up, and allows for editing while saving and opening, and an easy way to support an undo command.

Most text editors today do not support such functionality. With lockless data structures like an rrb-tree it becomes easy. It really is an ideal way to do write a text editor.