How do I add a Filter Results By subcategory dropdown menu to product list results?

[molywerks]

When customers make a category selection, instead of subcategory image/text links, I'd like to provide customers with a Filter Results By dropdown menu for any subcategories in addition to the filter by manufacturer dropdown.

What is it that I need to add (for at least the subcategories filter dropdown)?

I think I am on the right track in looking at includes\templates\template_default\templates\tpl_index_product_list.php. I probably need to copy and edit something there and then copy and edit something in the corresponding modules/functions file?

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A (more complicated?) request but ultimately the more elegant solution for my needs:

Ideally, instead of a subcategories dropdown, I'd prefer to add dropdowns for size, material and color, too. These are all fields I've added to the products table. So, I think that can be done eventually, but I'll have no clue how to go about that until I've taken some PHP classes. So, if a mod exists (that I've overlooked) or this is a relatively simple hack, I'll take your suggestions.

Thank you for any answers!

[Elk Hair Caddis]

I would really like to know how to do this also. I am building a store and doing this would really make it more user friendly.