Would it look funny to center the sideboard between the window and corner?

Hang a long and narrow mirror vertically on the other side of the sideboard. This will give the impression of a window and give you the symmetry you are looking for. Of course, you would probably want to then remove the mirror over the sideboard and hang a painting instead.

Another idea is to put a potted tree to the right of the sideboard. You want it taller than the top of the mirror.

Get over the symmetry and move the sideboard over so it's centered on the wall between the window and the corner!

No. I like the sideboard centered on the table and chandelier.

I agree that the sideboard can be centred on the wall. Let the curtain hang straight to the left of the window, and remove the rushes (?) in the right corner as they add no visual appeal.

ignore it and center the sideboard on the wall

I have used a tall floor mirror to balance my family room which has a similar set up. I don’t have a picture as I have a tv on the wall now.

I agree with just moving it over to be center on the wall.

I like Beverly's version of the mirror hung vertically and a tall plant in the corner.....or just nothing.....not every surface/floor needs something on it. What is bothering me most is your window treatments....can they hang straight down and to the side of your windows? Tied in the middle just doesn't look right to me. Your remodeled dining room does look nice.

Agree with Beverly's version as well.

I don't care for the way the chandelier and mirror overlap with each other from the angle in the first picture. I would put a painting in place of the mirror and have either a tall plant or a mirror that is close in dimension to the window on the right side.