Could you plant some evergreen trees at the house corner? It would take a while for them to grow tall enough to provide shade but that might be a long term goal with something else that might provide short term relief.

I do not agree I have a corner window with solar shades mine id not quite like yours but that small slit where the shades will meet is a heck of alot better than the whole window the rods go onthe ceiling

what did they do with the valence? Are you able to share a picture?

We did a few corner windows for a community in Florida. Here are some pix. We did bottom-up top-down shades as well as roller shades.

Boca Bridges and Lotus in Boca Raton, FL · More Info

Though you have no post between the glass panes, the shades will overlap with very little gap.

thanks for this. yes i can see how that works with cellular shades, but the problem with solar shades is the box/valence that houses the roll at the top, which enlarges the gap.