On the Dots, you can click and hold, then drag the route you want to take /Mark.
From Google Maps / help
Just tried it and it worked fine.To choose an alternate route, either click on a greyed-out route on the map or click on one of the other routes listed on the left-hand side menu. Note that you can also change routes by clicking on one and dragging it so that the directions will take you via certain roads.
I use the "Measure Distance' tool for something similar. Each click adds a dot, and at the same time gives you an idea of how far you'll travel.
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