I see a lot of empty Gin bottles in the dustbin!
Ya the corner is a terrible place but of course I have learned to mix there without issue, at least no ones said anything negative in the last 4 years. The monitors are actually closer to my ears by 1/3 the normal distance.
My original desk in my "real" studio had the monitors on a bridge so they were also as close as possible. Getting monitors close to your ears eliminates a lot of room interference. I don't have any treatment in this corner,,, the random clutter is it!
As far as placement of keyboards ( both types) I find under slung trays are to low to both type or play. They also get in the way when I play my guitars.
I like my computer keyboard right in front of the monitors. I've always had my midi keyboard off to one side normally at a 90 degree angle to the main desk. But I like the way it is now at the 45 degree angle so my new build will feature this somehow.