Bookmarklets are cool. They are just javascript functions in an anchor tag. Try these ones, and drag them into your bookmarks toolbar if you want to use them on other sites.
Advanced usage: most browsers allow you to set a 'keyword' for a bookmark so you can open it directly from the address bar. This allows you for example to type 'r' in the address bar and hit enter to quickly to drop into reader mode if you set up your bookmark that way.
If you're writing your own bookmarklet, this editor will escape all your javascript and minimize it. Handy! https://chriszarate.github.io/bookmarkleter/