Hello Malgorzata!
Right now we have special filters inside of Store Manager for OpenCart
for example, you can:
- to filter products by categories
- to filter products by conditions (by columns)
watch video -
http://screencast.com/t/TwQEh2RP
- you can filter products by name (or any field) in the column or by search form
watch video -
http://screencast.com/t/O71tEMih
Could you explain, what kind of module do you mean ? "opencart filter module"