This works as advertised. You know how great a complement this statement is in these dark times!

I have two suggestions:

1. As practically all other folks here are demanding, the sidebar must be wider. If this is because Side View uses the built-in side view pane in Firefox, please, if at all possible, implement your own side pane and make it wider.
In case that's possible, why not more than one side panes simutaneously? Keeping two sidebars at each side would be very nice.

2. The Side View icon on the quick menu that appears at the top right corner by default. Currently its only real function is to switch between mobile/desktop view.
Please add that command in the context menus. Currently it has only one item (Open in sidebar), please change it to something like 'Open as Desktop/Mobile Site in sidebar' - so that if you click an empty space or tab, you could also choose how it will load. Then we could unclutter the quick toolbar if we choose to without sacrifice. Keeping track of sidebar-only visit history can be nice to some people, but I find it not very crucial.