I really love using the sidebar for messenger but would love if the functionality could be added to other sites too. as it just seems to be using the standard website interface I don't see any reason that users can't customise their own pop out sites.
Having a pop out version of say Spotify, wikipedia, and BBC news (or other news service) would be awesome; those websites scale pretty well and would be useful to have quick access.
Take a given URL and then either detect the favicon of the page or have a user add their own custom icon, then create a pop out section with the set icon or favicon which is linked to the chosen page.
Thanks for the awesome work so far!