This is very useful when you have multiple monitors with different resolutions, and you want to have a different font size on each monitor. You may need to set the Window zoom which affects all windows to meet your needs on the main monitor, but then adjust the font zoom only on the secondary monitor to make it look right. I have a 4k 32" main monitor with a huge resolution of 3840 x 2160, making everything on it tiny, and a really old monitor with a tiny resolution of 1280 x 1024, making everything on it look huge. Now, I can use Editor Font Zoom Out repeatedly on the old monitor to make it zoom out enough that it's usable and still provides a really good size editor window.