This paper introduces Scylla, a toolkit for designing highly reconfigurable interaction within Smart Spaces. Using Scylla, users can define, edit and configure their interactions. Scylla's toolkit is part of our framework for studying and improving multimodal Human Environment Interaction (HEI). This article is in continuation with the work previously presented in [8]. In the first section of the paper, we describe our approach and the HEI framework. In the second section, we introduce Scylla that is part of the framework. We provide a use case and scenario that consist in building a HEI configuration using Scylla.