@Yoline, I am having the same problem.
I agree, it's annoying to have the page reload to the top each time a category is chosen.
I want my customers to easily switch between categories without having to scroll down from the top of the page each time.
Have you found an answer by contacting Squarespace support? Or have you privately emailed/messaged any of the community developers?
I'm surprised this question hasn't been asked and answered before.
I will contact Squarespace support when they are available. But I will directly ask some of the community developers... @tuanphan @rwp