Go to your user settings and uncheck "show read posts", I just recently found it so I dont know how it works exactly, but im assuming once you open a post it will be considered read, and hidden on mexr refresh

Second link works fine! the first doesnt

Yep, saving works good for that. But yeah, once you open or upvote it, theres no way to undo that, so they will get hidden with that setting off.