I have a Firefox instance that I set, with application rules, to always be in a certain place, with certain size, etc. I have another place where I want to fill it with another Firefox instance, with its own position, size, and all. I understand I can match application name "firefox" or title, but title would be dynamic based on the tabs I think. How should I do this? Right now what I do is just have Chromium as the other browser window, but it would be nicer to have the same browser. There should be a way to do this somehow.
What I've been doing to get around this is have an extension on Firefox that lets me change and persist the title. That way I can use per-title rules on each window.
You would need to somehow uniquely identify firefox instances. One way is to match the title, another option might be to specify other StartupWMClass or pass --name argument to firefox and then add a resource class match.