You can go in the settings and select it either to default to the speed limit or your current speed.
If you set it to use current speed, you can have it go up to speed limit if you half press down and hold on the right stalk or tap the speed limit sign on the screen.
If you set it to use speed limit, I don’t think there is a way to quickly have it go down to current speed. Just have to use the scroll wheel to reduce the set speed.