How to delete unused effects in Adv. Actions?

Hi

I am using CP 7.0.1.237.

I am playing around with effects in advanced actions. i have created several XML files of the custom effects and assigned them to my smartshape buttons in advanced actions. But after some time, the list has become very long and it now has many unused custom effects. Is there a way I can remove them from the Custom effects category?

Sreekanth