After logging off last night,
I played around with Win 8, 7 style skin.
I partially modded some parts to see how a scrollbar could work,
put second column as 128 alpha and dark grey brightness.
I put your picture behind menu to see what it looked like on Win 10.
(Win7 os has smaller blur radius)
I set small icons at 24 size.
Here is the screenshot.
It would be nice if you had a real screenshot, or your working on, skin file.
Ok, I understand you want the left column as blured frosty.
Frankly I don't even beleive it if you got it working with a programs tree on left, without a second column.
How would one shutdown system through menu?
I've been wrong before on stuff.
I remember when a coworker said passenger jet planes fly 5 miles above earth, until I looked it up.
Boy was I wrong. It always looked like a mile or less.
Anywhere from 8 to 11 miles high!
If it's the left you want frosty blur, I would not modify the menu bitmap below 64 alpha,
because from past experience, transparent parts of scroll don't work properly.
Hmm, if what you are using is really "Classic Skin.skin7", there are no menu bitmaps!
I have to go. Will get back to this site in evening. Bye.