ca. 2014 I was able to write a bookmarklet that scraped a twitter thread by accessing the DOM (even causing page navigation) and rendering it as a reply-tree.

Two things make this vastly more difficult now:

1. Twitter uses obfuscated css classes that appear to change on every deploy, which makes scraping hard.

2. You used to be able to get around the limit on bookmarklet code size by adding a script tag to the page and loading remote javascript. Now browsers respect HTTP headers that sites can use so that only scripts from whitelisted sites are loaded.