Embodiments include a method comprising providing a design interface that depicts a plurality of interface elements of an application under development, each element defined in source code accessible by the application development environment in a declarative markup language. The method can comprise receiving, through the design interface, data representing a selection of a plurality of the interface elements, identifying the declarative expressions corresponding to the selected interface elements, defining a new declarative expression, and generating at least one code segment using the identified declarative expressions. The method an comprise storing the generated code segment in a computer readable medium, with the stored code segment associated with the new declarative expression, so that the new declarative expression can be inserted into the source code in place of the identified declarative expressions and/or can used in a second application under development.