What makes this difficult to you? There are various ways to close a tab apart from clicking the close button or pressing Cmd+W on the currently selected tab. You can right-click the tab or middle-click the tab with the mouse wheel to close the tab. There is the tab manager (down arrow) button on the tab bar that allows to close a tab in its drop-down panel. There is the Firefox View button that allows to close a tab. *https://support.mozilla.org/en-US/kb/how-set-tab-pickup-firefox-view