As you have probably already read about in a couple of blog post from Jennifer Boriss, Dave Townsend, and Blair McBride, the next major version of Firefox will contain a shiny new Add-ons Manager. If you wanna know more details, you should check out the design documents.
Even with the development for this feature still in progress, Mozilla QA will hold a testday for exploratory testing the new user interface on Friday, April 30th. For this time we will not use any Litmus test but running tests based on the current test plan.
If you are interested in getting your fingers wet and to help us in making it a helpful and less buggy feature, read through the test day documentation and join us next Friday on IRC.