It is pointless to have a small amount of painted wall exposed between the window apron and baseboard. Remove the apron and replace with a flat stock from floor to sill for new apron. You can then base around it.

How tall is the new baseboard?

Trying to decide between 5 1/4 and 6 1/4. Area has rooms with 8 foot ceilings and also a large vaulted great room

Picture

As I mentioned, install square stock for apron all the way to the floor, then wrap it with baseboard.

Thanks when you say “wrap with baseboard do you mean butt up the baseboard on both sides of the flat stock or basevoard over the flat stock… also is flat stock just flat baseboard?

Baseboards installed around it : sides and front.

Flat stock is your standard 1 x whatever.

Ok gotcha, thank you G&S. Here’s a quick mock think it will look weird?

Mock

Mockup from some scraps

Looks good!