I don't use CSP, but setting layer thumbnails to crop out the transparent areas around the layer content is a common setting for art programs to have. Looking it up, it seems like this is how you do it: https://ask.clip-studio.com/en-us/detail?id=16666

"There is a tab written as "◇ Layer" at the top of the layer palette,
I think there is a small icon of "▶ three" on the left side.
Click there and select "From thumbnail display setting"
Please uncheck "Show transparent part"."

Granted, this thread is from 6 years ago, and Google translated from Japanese, so things might be different. I'm guessing you can probably just do what Victoria said except go under "Thumbnail display settings" instead.