Bookmarks app- can’t add bookmarks on mobile browser

When running the Bookmarks app on a mobile browser (e.g., Safari or Firefox on iPad), the panel (on the left) with the button to add a bookmark does not appear. This works fine on a computer. Is there someway to view this panel or is this a bug?

There should be a hamburger menu icon in the top left corner of the app which allows you to open the navigation bar.