At present, if multiple errors show up, you have to close them individually. Personally, they're all usually always related, ie they're either multiple artifacts that have failed because a build failed (one error per artifact) or we have a server space issue and every build throws an error about it. In any case, if all the issues have been dealt with, it would much nicer to be able to clear all the errors in one swoop rather than having to clear each one individually.