Changing Firefox's Open Containing Folder action

I've just installed Enlightenment on my Mint desktop and am loving it. But when I download something from Firefox, then click on "open Containing Folder" (in the Firefox download menu) the entire screen becomes unresponsive until I switch to text console and kill Firefox. In the default desktop (Mate) this action brings up the Caja file manager. I can start and run Caja under enlightenment. Ideally I'd want to use the native Enlightenment file manager, but would be happy with any workable solution which did not freeze my screen. I believe that the action is mapped by the desktop mimetype settings - but I can't find any way to edit that within Enlightenment.