You have an extraordinary amount of relationship properties between your different collections. So when you click that arrow in the builder, it needs to load up every single option to display them to you. This takes a lot of processing power and can cause the browser to not respond.
We are working on improving these performance issues but a fix for this may be a while away still. My only suggestion is to close everything else on your computer and only have this open in the hopes the computer will have the processing power needed to open that option.
Your only other alternative is to rethink your database design and try to cut down on how many relationships you use.