There is this. In the thread display, click on the circle on a marked as unread thread (star if you participated in it) to jump to the first unread post. This circle isn't there if there are no unread posts. Similar behavior if you click on a notification: "posted a post in X" -> brings you to the post. "reacted to your post in X" -> brings you to the reply someone reacted to.
Apart from that, there are a few shortcuts for the editor, for example hold ctrl and right click for some more options. Haven't seen anything useful otherwise, even after years of usage.
A useful feature are activity streams. They let you control which kinds of posts you'd like to see: What kind, from whom, in which forums, etc. Five are already there, the Unread stream being the most useful I think, the others are things like posts you created or the content you posted in.
You could try looking for some kind of a manual on the developer's website (name of the board is InvisionPower Board, IP.Board or IPS). Link is in the footer of AirVPN's website (the CMS by IPS part).