The top bar held a search box that looked across screens, content and playlists at once, and a New menu for creating things from anywhere. Both are gone with the bar, and neither has a replacement in the sidebar.
Each section still has its own search, which is where most searching happened: Screens, Content and Playlists all filter their own lists, and those searches know about the things particular to them, such as labels on screens. Creating things still starts from the section you want it in.
If you leaned on the global box to jump between sections by name, this is a step back for you specifically, and worth telling us about.