Following Gigazelle's advice, open up a flow visualization and start with your "thank you" page. Then drop in your last touch channel dimension on the left. Then you could also drop in your first touch channel dimension to the left of that to get a clean flow of visitors that flow from one entry campaign to another closing campaign.
Marketing Channels would be the closest way to get that data, however that specific visualization is currently not available within the tool. It also only does first/last touch, instead of all channels.