xF2 Add-on [XFI] Categories - collapse & expand 2.1.0

Addition will allow your users to give the opportunity to collapse / expand categories.

Also there is the possibility to exclude certain categories for folding.
But, this is done in the style settings, where in order to exclude the necessary categories, you just need to specify their IDs separated by commas.

There are also group rights that allow you to disable this feature to a specific group.