Edit Mark As Complete Button

hi, I need help to edit the mark as complete button. A lot of people of our course Couldn’t find the button sometime and dont understand it as when the do the course from pc. As the button is in top left corner with the same color as the top bar. Is it possible to edit the button color and also can I place the button in bottom side? If that button cant be edit then is it possible to add another mark as complete button on the bottom side beside next button. It would ne easier for students to see it.

The page I need help with: [log in to see the link]