Do that by creating a file with a unique name for you this will have to be the same as you chose for your em:id value in your install.
Firefox will also notify you if a restart is required to use your new extension.
You can block sites within fixed time periods e.
However, I need to find where is a particular extension say, located; the problem is that most of the extension folders are named by guid, e.
Either use or host it yourself.
You can adjust when and how you want to discard these tabs effortlessly as well.