Useful inheritances from scientific experience open perspective ways for increasing the degree of success in designing of systems with software. One such way is a search and build applied theory that takes into account the nature of design and the specificity of software engineering. This paper presents a substantially evolutionary approach to creating the project theories, the application of which leads to positive effects that are traditionally expected from theorizing. Any implementation of the approach is based on a reflection by designers of an operational space of designing onto a semantic memory of a question-answer type. One of the results of such reflection is a system of question-answer nets, the nodes of which register facts of interactions of designers with accessible experience. A set of such facts is used by designers for creating and using the theory that belongs to the new subclass of Grounded Theories. This sub-class is oriented on organizationally behavioral features of a project's work based on design thinking, automated mental imagination, and thought experimenting that facilitate increasing the degree of controlled intellectualization in the design process and, correspondingly, increasing the degree of success in the development of software-intensive systems.