Firefox developers are exploring ways to improve support for web apps, including generating a unique app_id and class-instance for each launched site. This would allow for better management and organization of web applications on the browser. Some users suggest that a privileged extension could be used to achieve this, while others propose using a combination of JavaScript and bash scripts to monitor window titles and move them to specific workspaces.

Source: https://connect.mozilla.org/t5/discussions/how-can-firefox-create-the-best-support-for-web-apps-on-the/td-p/60561