I poked around a bit on Discourse’s own forum and found this trick where you can move the left sidebar up to the top as a drop-down hamburger menu just by adding navigation_menu=header_dropdown to the URL. With that setting, you don’t waste any space on the left with the sidebar.
Thanks, but it doesn’t make use of the extra space, it just shifts the content to the left. And makes the text section not centered (I prefer it centered). This is same as when clicking the hamburger button to hide the sidebar.
Initially I had the sidebar hidden but then realized the space is wasted anyway, and now I had an extra click if I wanted to use the sidebar links.
The setting is unfortunately not persistent. It works as long as the navigation between the pages is still done with JS. As soon as when you click on the logo (so that the page returns to https://forum.mikrotik.com/), and press F5 or something similar to refresh the page (or open https://forum.mikrotik.com/ in new tab), everything reverts to the old behavior.
The sidebar did move into the menu. I was just saying that the space that the sidebar used to occupy is replaced with white blank space (after shifting the central element with posts to the left). It doesn’t increase the amount of data displayed on the screen. If you use custom CSS, maybe it does.