Boox Color Series User Manual page 116

Navigation Ball
Navigation Ball is a circular ball that floats above all the apps on the screen.
9 buttons can be customized.
Single click on the ball to expand and collapse navigation menu.
It requires to turn off and on again after the new button settings.
The Navigation Ball by fault is in Fan-shaped style. You can choose other
display styles ( Horizontal Style, Vertical Style) from Navigation Setting.
You can also adjust the transparency of the Navigation Ball.
This supports to set as a resident button. After being set as a resident
button, the button will always be floating on the top layer;