How do I access extras-developers builder? Want to try out version 4. Alternatively, when will version 4 be available in extras-developers?

Also is there a way to just copy dockbars? I am using 9 desktops and it is proving a pain having to fill out the 8 spaces, 9 different times. Would like to be able to just do it once and then each new dockbar I create has those 8 things in by default.

And I am sure it has been mentioned before but what does the set image option do?