I would start by working out the sectional profile vertically and horizontally. It looks quite complicated because the chamfers vary around the inner window surround and the outer one. If they were consistent, it would be an obvious job for Follow Me. I suspect it may still be a Follow Me job for the outer surround followed by some editing of the elongated top chamfer.
The inner surround looks to be square edged except at the bottom.
I’ve tried to repeat your steps but don’t getting it worked with the scale tool to make the tapered sides.
The example you made is not the same size as the window.skp example.
Is there any way you would make it in the same size? Would appreciate it alot since I’m frustrating myself 2 days on this single window thing