Yes, since Eddy there has been a lot of successful tri-tether multi-body kite history. We are not done reviewing nor advancing the art. The only conceded intractability is the formal abstract mathematical chaos.
Its the statistical survival of multiple rigid wing kites for AWES that remains an open question, especially in the context of those systems dependent on multi-body computation. They are already able to show nominal operation. The problem is any exception-handling for which an algorithm lacks a critical response. Complex multi-kite uncertainty is not easily tractable by current automation computation. Look at self-driving car limitations. This does not mean permanently intractable, just very hard.
As for related multi-body prior art, interplanetary orbital mechanics is the original similarity problem. Then came atomic and molecular dynamics, robotics, and many other engineering science domains; and now AWES.
An ideal multi-body AWES system would have inherent dynamic stability across a wide range of load and wind conditions. Digital sensing and actuation is suitable to support the supervisory pilot role (as long as pilots are required by regulations), especially to servo-activate major state transitions, like sense-and-avoid airspace emergency.