An interactive platform supports multi-user participation in a shared virtual workspace to prepare and schedule virtual print trays for printing on a three-dimensional (3D) printer or other fabrication resource. Computerized models may be automatically positioned within the print tray, manually positioned within the print tray, or some combination of these. After objects are placed in the virtual workspace users may be given identity-based control of the print tray including, e.g., identity-specific capabilities for viewing, modifying or removing objects within the print tray. This permits improved control over aspects of interest to particular users including, e.g., security, object orientation, priority, fabrication speed, fabrication cost, and so forth within a shared fabrication environment.