Username/Password save and auto-fill is governed and saved in the internet browser, not FBO One.
Setting is enabled. Username and password are autofilled on page load for the login page
Setting is disabled. Username and password are not autofilled on page load for the login page. Saved credientials may still be available from the browser.
Please note this setting is not available per FBO in the 'FBO Locations settings' page area.