There are currently 4 options shown in the settings menu on the top right of the page.
Dark mode/light mode: changes the colour setting of the website.
Traditional/new bet slip: this only affects lay bet slips by alternating if the user input is backer's stake (traditional) or the laying bettor's risk (new).
Football/soccer: shows either "football" or "soccer" in the sport nav menu.
Decimal/American odds: changes the UI odds display between decimal (1.5/3.0) and American odds (-200/+200). This only affects the UI display of odds. Only decimal odds is used in backend calculations. Currently, bet slips must be submitted using decimal odds, regardless of this setting. Clicking a cell with American odds will automatically populate the bet slip with the correct corresponding decimal odds.