If you want a TV there, I'd get a small flat screen and mount it on a wall or sloped ceiling. Then clean out everything in that dormer. Then get a movable (on wheels) room divider, cover with insulation board covered with flannel. That way it could be moved for best lighting and view from sewing area.
At a class one time, wall space was a premium. One person hung a flannel sheet over a window. Because it wasn't held taunt, it moved constantly and nothing would stay attached to it if not pinned in place.