Well, here are some ideas anyway, from Joseph Nye, a professor at Harvard. The basic idea is to “establish rules-based international institutions with different membership for different issues.” In other words, isolate issues and then try to form groups that will be able to reach consensus on each narrow issue.

• Countries like Russia and China are likely to accept a return to the idea of respect for sovereignty as defined in the UN charter. This allows some bad things to happen within borders, of course, and doesn’t solve disputed borders, but it used to limit cross-border military action and allow for joint international peace keeping missions in smaller troubled countries in less strategic areas.
• Reboot the World Trade Organization with new international rules rather than bilateral or regional agreements.
• Continue international financial cooperation, which he says is actually a bright spot.
• “International ecological cooperation” – he says this has to override sovereignty. Not a lot of specifics here, but a return to the climate treaty and reinvigorating the WHO would certainly be a starting point. I would suggest we need to start taking biodiversity seriously, and also have a look at the long-term stability of the global food supply. Surely this last is something everyone can agree on?
• Cyberspace – not a lot of specifics, but new agreements and norms are needed. Nuclear and biological weapons are not mentioned, and in fact weapons in general are not mentioned (drones, autonomous weapons, missiles, mines, space weapons?), and I would suggest adding these. Anything that will reduce risk in the short term will buy time to figure out a long term plan to give our species and civilization to make it.