Custom css themes shouldn't be too difficult. Probably pass in a url parameter for the them you want and then handle it in the template. Night mode has been requested.

ToolbarScrollingKiwixWebView is in java
Convert it into kotlin

The wikipedia api provides a section an id (1 upwards), it'd be nice if that would also be included.

Example: https://en.wikipedia.org/w/api.php?format=xml&action=parse&prop=sections&page=License

Use new presets

The bookmark sidebar display is linked with the swipe left-right gesture. On ipad this happen even if the swipe is done at the really right of the screen (but the side ar appears in the left).

This compete with the video player progression bar used to seek and therefore pretty annoying.

I propose that this gesture applies only on the really left of the screen.