If you pin tabs, they'll be loaded on start and stay until you close them. Always in sight even if you have a lot of tabs. At least on Firefox.
It seems like this would almost perfectly act as a "predefined list of pages always open to the side, especially for real-time communication" or did I miss something? It won't be next to the page, but always visible at the top-left and kept between restarts.
I know pinned tabs, I pin the music tab, it plays in the background, I never have to look at it, cool.
The point of having slack/mattermost/discord/whatever always on the side is that one does not have to switch away from the main tab just to see what's going on.
It seems like this would almost perfectly act as a "predefined list of pages always open to the side, especially for real-time communication" or did I miss something? It won't be next to the page, but always visible at the top-left and kept between restarts.