You want to search out FileMaker Master Detail. In this example, I used a global field for the relationship, and a script that actually performs a find. Hopefully someone else can have an easier method.
You have to unzip ("Extract All")
What you describe should work just fine. Go To related records should take you to the record clicked in the portal. The fact that you are using a Cartesian self join will not keep it from working.
Be sure to specify the "Show only related records" option.
Go To Related Record [Show only related records; From table: CustomerListPortalTable; Using layout: "YourLayoutHEre" (MainCustomerDetailsTable) ]
All sorted - it turned out to be a layout issue rather than joins or scripts, which are all fine anyway.
The idea of the listing portal is that it sits to the right of the main screen, like a widget. I had it slightly too far to the right. When I moved it into the middle of the layout to test it, it worked fine. So for some reason, you need the portal actually with some credible piece of it actually on the main layout to work. I just had it set up too skinny!
Perhaps instead of "too far to the right"--that doesn't really make sense, it was "too high"--touching or crossing the header-body part boundary.