This flag, which is set to true by default, enables client-side timeout monitoring. The client-side timeout value is synchronized with the server-side session timeout value provided in the HTTP server configuration. When client-side timeout monitoring is enabled, the browser keeps the session alive by sending signals to the server if the user continues to be active (moves the mouse, uses the keyboard, or initiates touch events on a mobile device). When client-side timeout monitoring is disabled, the session is only kept alive when the user submits the screen, and therefore the user may timeout even if they are actively typing or clicking around on a screen.
Where do you save this configuration option? Here.