The menu's aren't really that hard to figure out as some are letting on if you are just paying attention a little bit.
The top menu is constant with the only change seen is when the display area is narrow and some of the items are put into the 3 bar menu so all of them are available... other than that, it stays pretty much the same.
The menu area just below it... call it the secondary menu is area specific. So if you are the main forum, it'll contain items relevant to forum posts like the "Watched Thread", Watched forum" etc... in the Conversations area it has actions related to the Conversations. As the area is narrowed down... the other items that can't fit on the screen are placed onto the ellipse menu ( ie 3 dots like ... )
Well, it's not quite that simple. The "New posts" button should be available on every screen, but it's not (it's not there when looking at a profile, or alerts, or a conversation, for example
I, and others, are paying attention and do have them figured out, but menu's and sub-menu's that need to be visible for ease of use, somtimes aren't.