My friends are mid-renovation and just sent pics of their new quartz. They chose to keep their window trim and install what looks like a short 2" backsplash on their window wall. It works in their kitchen because the range is on a separate wall (in an L shape) so it looks good to have a short bs on one wall perpendicular to a wall full of tile on the range wall.

I would probably work with what's there.I think the bamboo shades are the odd element with the cocoa color. That's not what your question is. But with a different shade or blind treatment, the wood trim, as a natural element, with soapstone it will all "pop"...in a good way. I wouldn't alter the trim one bit. Get the 4 in soapstone splash, keep trim, and plan for some new blinds/shades would be my plan. Wait and see the hue of soapstone with the light , after it's installed.

I would install a soapstone backsplash in that corner & end it at the end of the windows. You can tile everywhere else.