It is very common that the clients enable course custom fields as filter which is very useful.

But it can be a problem or challenge if there are several custom fields and several subcategories every category (custom field). It ends up in a very very long list of filter on the left side of catalogue. please see the attached image.

It would be much more easier to use the filter if it is possible to collapse and expand categories and still be able to choose several subcategory in the same category.