On later iterations of the Peugeot 308 featuring piano-key style physical toggle buttons below the screen, the method requires a passcode:

unless you know exactly what they do, as changing system parameters blindly can glitch your navigation, audio balance, or infotainment operating system.

You cannot disable Stop/Start via the normal menu on most 308s. However, inside the secret menu under "Electrical Parameters," there is a field called "Battery State of Charge."