I'd like to create a Hotkey that will minimize ALL the windows of a given class or with a given title. I've tried this with the one.dll module.

after (finally figuring out how to use the !One bang
my command looks like this (without assigning a hotkey yet)

!One [MozillaUIWindowClass][][.none][.minimize][.minimize]

This works but only on one window at a time. If I have two instances of Firefox running (or whatever other program) it only minimizes one and I have to do the bang for each window

Can this be done simultaneously for all instances of Firefox?

Is there another module that does this?

I dont see any way doing this (without python ;). You could ask the One authors to add some "all" flag handlich that stuff to their module ...

Why would you need to close multiples of firefox?
FF is a multi tabbed browser.
Unless you are just using this as an example I would understand.

One.dll would do the trick no problem.
Just create a loop script that closes them and hand it to the hotkey.