It works, has settings to manage auto-opening in Web App Mode, and has a settings to control the size of the window plus the position. I have yet to find an issue with this.

Hey, thank you very much for this addon. It is perfect. I was also looking for how to match the window I am openning from command line (or windows taskbar) and luckily I've found solution to my problem. Posted here: https://github.com/ettoolong/WebAppMode/issues/1

Fantastic addon. I hope this stays maintained.
With a bit of my own work, I used it to create desktop-embedded webpages. With the required "popup window" addon I can just right click a page and send it off to it's own little container on the desktop with no taskbar or switcher entry.