Trimming Stairs at a Straight Angle at an End

[DishingTech]

I have an interesting issue regards to changing the steps. I have wrapped the stairs around the angle of the deck which I am happy with. It is a bit hard to explain but I will have a go.

However, I would like to have the steps stop at the blue vertical line on the left hand side so that the steps are inline with the left hand side of the deck.

To visualise it better, imagine having the stairs go past that blue vertical line and having that blue vertical line be the cut line. Removing what is on the left hand side of the stairs.

How can I go about doing this?

Thanks