A comprehensive software development process needs some adjustment before it can be used: It needs to be tailored to the particular organization's and project's setting. The definition of an appropriate tailoring model is a critical task. Process users need tailoring that enables them to trim the process to reflect the actual needs. Process engineers need a method and a tool to define a valid model. The SE Book of T-Systems contains a feature model to describe variable parts of the process model and relations and constraints between these parts. The notation and semantics of feature models can be used to visually author a consistent and valid tailoring model. In this paper we present a tool for visual modeling and validation of process model tailoring based on feature models using the SE Book of T-Systems as an example. The tool is based on a domain-specific language that represents the process model. It leverages the semantics of feature models to provide an easy-to-use editor for tailoring-enabled process models.