As I built a custom TOC for a project a few months ago, I found that a nice feature, besides automatically updating the TOC, was the option to override the text of a particular entry (either because it was too big for a sidebar item or for whatever reason). To see what I mean, here's how it works on the backend: https://www.dropbox.com/s/fi1x80zp5z6ml65/gutenberg-toc.mp4?dl=0 (wait until the end).