Those plants can tolerate cutting back to 50% of its size in the summer in addition to Winter coppicing, but that may still be too tall for your needs. It would probably be easier to replace with a variety that is more low-growing.

They're easy to grow from cuttings. You could start some new ones and plant them elsewhere.

Unpruned Buddleja davidii have sometimes been seen 20 ft. tall in Seattle - yours is just always going to be a problem as long as it remains right in front of your window.

In the Spring, cut the tender shoots right at the base of the bush when about 4 inches long. They root very easily.

You could move it somewhere else.

I agree you could move it. I just transplanted one almost this size. And it survived after a slight wilt.

Sue, How tall does your plant bloom? will ot bloom if four foot tall, or is it a sox foot beast beauty like mine?

I grew mine from an unknown twig that I rooted. But I think it might be "Blue Knight", still not sure. I have even seen them with wrong tags for sale. It bloomed since it was only about only 4 inches tall and had just gotten roots! First year it was about 4 feet and this year it was about 6 feet tall, with some huge new shoots later in the summer. It was about 6 foot tall whenI dug it up and moved it...it wilted then perked back up fully.