Thumbnail size per folder


When saving a folder format (let's say showing images as thumbnails in images folder), how can I force the thumbnail size to 256 by default for said folder? It always resets to default when I restart the program.
I know about how to change the default setting, but I'd like to be able to change the setting on a per folder basis (and retain it).

I think these are the best posts/threads on this, at least that I can find:

OK, I will try this.