There’s a detailed history window? The sidebar isn’t it; just a quick overview. Control+Shift+H for the full history screen. It’s also in the menus under history, at the bottom. Like the full bookmark window is control+shift+B and linked at the bottom of the bookmarks menu.
Control+Shift+H or you can find the link to it in the history menu in the main Firefox menu. Or at the bottom of the history menu from the history button if you add it to your toolbar. Or in the Library section if you use that menu/button.
The sidebar is a cut down overview.
Same for bookmarks, the full bookmark screen has more depth and features than the sidebar.