Thanks for this
Testing on my localhost it seems to work great for adding a text sidebar to the "list" pages.
Minor "bug", on the Admin Setting page I was getting a wonky looking
en.sidebar_settings menu button.
I don't know if you wanted it to have it's own button or be under the "plugins" button, but I think some simple config/ YAML tweaks should fix thinks up nicely.
# sidebar_settings: 'Sidebar Settings'