Can add "customise" to the watch face?

In Samsung’s own watch face, there is a “customise” button when you long pressed on the watch face - upon tapping that button, you can use the bezel to change setting etc.

I am writing web-based watch face, is it possible to have similar feature?

The watch faces that are installed with the watch use an API that is not public. As far as I know it isn’t available to Tizen Developers.

Samsung Developer Program