@Fellfrosch and @mosen - looks great, let's go for the red dot.

That dot can be positioned as in @Fellfrosch proposal. We have 10% padding of the icon width between icon rectangle angle and the button border. I will be able to position that as an extra overlay in the button.

With the scale, maybe the dot will have to be moved - not sure whether it will overlap with the text. That I'll have to see in the code.

Red, as a color, should be in sufficient contrast with white and black backgrounds used for buttons.

As for compass, do we actually need it? Its the one that is going to be shine all the way while you drive along your route (compass is shown always when map is not pointing towards north). Maybe I will just dim it over some grace time, so the red will be less disturbing. But this we can see when we try in practice.