Maximizing (not fulll screen) safari window in Bug Sur not working (Option Click Plus) I am using Big Sur. Inside the Messages app when I click the green circle in the upper left hand corner while holding the Option key the green icon will display a black plus (+) sign and the window will maximize to take up the whole screen except the dock and the menu bar. I call this Maximizing the window.
This same functionality does not work in Safari. In Safari I use the same key combination and the green circle shows a plus (+) symbol when the mouse hovers over the icon, however when I click the Safari window does not expand all the way. It only uses about 60% of the horizontal area of the screen instead of the full 100% of the horizontal area.
Is there a way to correct this? It is very annoying to have to manually drag the edges of Safari to fill up the screen.
If you hover over green circle while not in full screen you should see following options:

'Zoom' is the option which should deliver result you are calling 'Maximizing the window'. These options are also available under 'Window' on Menu bar (by default keyboard shortcuts are for Tile Left/Right, others must be set).
Shortcut for Full screen is ⌃ + ⌘ + F. Using it while in Full screen reverts window back to initial size before going fullscreen.