A design engineer is an engineer focused on the engineering design process in any of the various engineering disciplines (including civil, mechanical, electrical, chemical, textiles, aerospace, nuclear, manufacturing, systems, and structural /building/architectural) and design disciplines like Human-Computer Interaction. Design engineers tend to work on products and systems that involve adapting and using complex scientific and mathematical techniques. The emphasis tends to be on utilizing engineering physics and other applied sciences to develop solutions for society.
A design engineer usually works with a team of other engineers and other types of designers (e.g. industrial designers), to develop conceptual and detailed designs that ensure a product functions, performs, and is fit for its purpose. They may also work with marketers to develop the product concept and specifications to meet customer needs, and may direct the design effort. In many engineering areas, a distinction is made between the "design engineer" and other engineering roles (e.g. planning engineer, project engineer, test engineer). Analysis tends to play a larger role for the latter areas, while synthesis is more paramount for the former; nevertheless, all such roles are technically part of the overall engineering design process.
When an engineering project involves public safety, design engineers involved are often required to be licensed - for example, as a Professional Engineer (in the U.S. and Canada). There is often an "industrial exemption" for engineers working on project only internally to their organization, although the scope and conditions of such exemptions vary widely across jurisdictions.
Work in progress...