The correct solution was given above, but I think it missed one step. Unless you uninstall Messenger first, Chrome won't give you the option (at least for me)
- Go to "add or remove programs" in Windows settings and uninstall messenger.
- Open chrome
- Go to messenger.com -- login if needed
- Click 3 dots on upper right
- Look for Cast, save, and share
- Click Install page as app
The good news is, because the app is just an edge browser, using a Chrome browser it will look exactly the same as the app, except for being Chrome. Well... you may need to do Ctrl-scroll wheel to change the zoom level, or Ctrl-+ and -
I'm also confused about this, because the three dots I'm seeing are for Messenger conversation info. I'm using Vivaldi, which is a Chromium browser, so if what you're describing is a function of Chrome specifically, then I can just look up how to potentially do this in my own browser.
Otherwise, the method of downloading an older version doesn't seem to work anymore, it just gets me a copy of Messenger that has an overlay telling me I have to update to keep using it, which I can only make go away by hitting the button and then actually updating it (by installing the garbage version through Edge). This is so frustrating, because this is how my mom and I communicate.