I'd like to show another app's windows under my app's taskbar button. It's a background app that reports another process's windows as my app's own. Is there any universal way to do this, e.g. each "new" window, alert glow, progressmeter, and other taskbar features, show under my own app's button?

For example, Winfox runs under its own process and steals Firefox's windows. It also adds features, but that's irrelevant -- I just want to support another app's existing taskbar features under my own app's button -- multiple windows, progressmeter, alert flashing, error flashing, mini-icons, etc. Is there a near-universal way to steal an app, or is it largely app-specific? Thanks!