Possible option for "framing" the window in the play area with functional storage, would also add pillows to bench area since window is not as low, and add crown molding to make it appear more built-in
Ikea Kallax hack for baby room
Great Montessori toddler bedroom - with an Ikea 2 x 2 Kallax hack (to turn into a toddler closet!)
9 DIYs That Prove Kallax Shelves Are Ikea's Most Versatile Product Ever
And Who Says You Can't?: TOP 10 IKEA HACKS / REVAMPS THAT EVEN YOU CAN DO!!
Instructions on making fabric cover for ikea drona bin for expedit