If you close all the windows of an application and don’t use it for a while, you may see it disappear from the Dock and from the Application Switcher. The application isn’t fully quit (at least not immediately), but requires you to open it again in order to use it. This macOS feature is called Automatic Application Termination.
Application Wizard lets you decide whether showing or not showing automatically terminated applications in the Quit and Switch menus. Including automatically terminated applications in the Quit and Switch menus allows you to effectively quit them or quickly make them active without having to reopen them.
Open the Application Wizard pane in System Preferences and click Menus.
To show automatically terminated applications in the Quit and Switch menus, select the ”Include automatically terminated applications in” checkbox and choose Running Applications from the pop-up menu. Automatically terminated applications will appear with a dimmed icon.
To show automatically terminated applications in the Background Processes submenu of the Quit menu, select the ”Include automatically terminated applications in” checkbox and choose Background Processes from the pop-up menu.
By default, the Quit menu doesn’t display background processes, but you can add the Background Processes item to the menu.
Open the Application Wizard pane in System Preferences, click Menus, and deselect the ”Include automatically terminated applications in” checkbox.