I have always been able to use the Mac setting to Double Click Title Bar to Minimize windows and it's always worked fine with Firefox. Until Sonoma, but with a stipulation. It will not respond at all to a double click, but '''ONLY''' when I have chosen to show the title bar in Firefox. It works fine clicking in the tab plane as long as I have Show title bar turned off. This is a bit bizarre, but it appears a recent update of Firefox no longer works like that in Sonoma. Works fine on a Windows 10 machine and on a Mac running an older OS. Note that I did do all the proper troubleshooting, reset Firefox, start in safe mode and all to no avail. When Show Title Bar is turned on, double click to minimize simply does not work.