Six Sigma led to Lean Six Sigma, which lead to Design for Lean Six Sigma (DfLSS). There is an exploratory component to DfLSS called DMEDI, that perhaps comes closest to open-ended, creative design thinking. It is supposed to be a complement to the more goal-directed component, DMAIC.

But fundamentally, both LSS and DfLSS are highly procedural and codified systems, and by their very nature, I personally believe, they cannot lead to effective design thinking. They share this weakness with other attempts to cofidy creativity, such as TRIZ.

Once you've bootstrapped your way a few degrees beyond "paper napkin" these methods can kick in and help in SOME situations, not all. But it is my firm belief that truly "original" creativity can only arise from chaos, randomness and methodological anarchy. There is a well-developed philosophy behind this viewpoint, and the best known articulation of it is Paul Feyerabend's classic, "Against Method."

This view has made me more than a few enemies, so be careful about adopting it, and if you do adopt it, be careful about how open you are with these views. DfLSS has acquired the status of a theology across a lot of mainstream industry.