Also I don't think that settings mark in the right corner should redirect to admin settings page. I think it should maybe lead to page which allows to change theme from dark to light or maybe to clean history. But it leads to admin settings entry page.
For admins better to create separate page which isn't available for everyone who just click on this button, maybe more securely.
Also if it sees that my account isn't admin it should just give access denied without additional

Open this page via a PHP-capable server, not file://.