The top menu seems to be holding too many concepts that don’t actually have much in common which makes then entire top menu feel inconsistent.
New, Unread, Posted and Top all respect the current selected category / sub category and filter
Latest and Category seem to provide alternative views over the selected category / sub category. At least I think this is how Category is intended to function. However category (along with the nav elements below) disappears when you navigate in to a category which has me questioning its intended function.
BookMarks, and Custom assigned Categories are navigation elements to take you to different parts of the site. Since they don’t respect or have any notion of the context of the currently selected category they feel like they should managed separately.
By breaking these up, I suggest separate options in the settings page and individually rendering separate div elements where we currently only render the “navigation-bar” div so that they can be easily customized as the separate concepts they seem to be.
This in my opinion, based on my shallow (not diving in to the source code) understanding, would make it easier to:
tackle concerns about nav elements disappearing when we go in to a topic view Discourse Meta because you have the option to remove just the category selector and filter.
add custom views by have a consistent means to inject alternate view navigation in to a Category Views concept that would automatically pick up the behaviors off all elements in that shared DIV.
offer slightly simpler way to make the elements seem more consistent in there behavior through styling since you can apply it to the entire div set of like concepts rather than each individual link.