Contrib Name + Repository ?
Same place as all contribs are for testing.
We don't generally publicise them because SME is currently still Alpha and there have been massive ongoing changes that break things overnight.
We just haven't got enough time to support general queries on stuff breaking in Alpha when the answer will probably be down to some breaking change.
It is far too easy right now to break your install by making a small mistake.
We will start releasing contribs to the contribs repo after things have stabilised with a Beta and we can then fully re-test contribs against it.
If you want to help properly *test* something specifically just talk to us on Rocket in the development team and we can guide you.
You have an account......