You can find it in the "Local Settings" section in the settings. If you are on mobile, you have to scroll down from the settings block. Also you may need to clear caches.
Note:
These options are kept on the device and are not synchronized between devices.
Can the local settings be made accessible without logging in? Perhaps in the sidebar/triple-bar/hamburger menu, where Search search lives.
(As a side note: the alt text for this hamburger menu button currently reads 'Expand here', which could be changed to better describe the action like 'Expand Menu' or 'Show Menu' or even 'Expand Menu here')