+Filter offers the possibility to sorting products after categories, stock status and manufacturer on the administration side.

Is easy to install with vqmod.
Here are the links for demo.
Frontend = http://www.op1.micportal.ro/
Backend = http://www.op1.micportal.ro/admin/

USER : demo3
PASS : demo3

If you have trouble with opencart you can find me here at nica.dumitru[@]gmail.com :)

Here You can find my plugins here https://www.opencart.com/index.php?route=marketplace/extension&filter_member=nicu78