In case if someone of you are not in Iota Rocketchat:

I'm adding multisignatures now. It was scheduled on this week assuming that we have already tested ordinary signatures. Because of address reuse double redesign we haven't tested the ordinary signatures properly, but I try to stick to the schedule, so we'll have to test them both simultaneously. GUI won't support multisignatures, they are not for casual users, only those who are fluent in API can help.