@kaa Touched on them in a follow up comment above, but here is a little more detail:
First is a simple markdown link button. Adds the necessary markdown around a highlighted word. If there’s a link on the clipboard, it inserts it as well.
Next is Title Case. I use it when posting something with a Title. I always forget which small words should be capitalized.
Last is markdown footnotes. Adds the inline and end-of-post markdown at once.