UMI3D is a recent model which allows the generic description of 3D environments through a network. These generic environments can run outside of any device, on a server or on a separate computer. A unique dedicated application that we have named UMI3D client allows a VR, AR or MR device to interact with all the existing UMI3D environments. Moreover, the client-server architecture allows these environments to be collaborative.In this paper, we introduce a toolbox which allows the creation and running of UMI3D collaborative environments using Unity 3D. It contains tools to address the main concerns of computer-supported cooperative work (CSCW) systems in UMI3D environments. After introducing the contribution of this toolbox to the design of 3D CSCW systems, we present a user evaluation of an environment designed with this toolbox. Finally, we discuss the limits of the UMI3D model and the improvements that could be made to this model.