This work aims to explore the application potential of utilizing the rich medium of olfaction in Immersive Virtual Experiences (IVEs) by engaging a broader range of non-expert users. Considering the inherent properties of scent (e.g., the absence of base odors and storage challenges) and the diverse application demands in IVEs, we introduce OdorCarousel. This design tool encompasses (1) a tiny, lightweight odor-emitting device that integrates with VR headsets and can store 25 distinct aromas. We conducted user-involved technical tests on scent release performance, focusing on identifying odor type, intensity, and transitions. (2) Based on two types of smell interactions in IVEs (active and passive), we devised and implemented three Unreal Engine-based olfactory interaction blueprints and user interfaces facilitating design. A case study illustrates the operation and design process of using OdorCarousel. We recruited 17 participants for a workshop-based user study, successfully executing six concept designs validating the usability and feasibility of OdorCarousel. Finally, we analyzed the design results and the olfactory interaction intentions, discussing the multi-dimensional potential and considerations of smell-enhanced virtual experiences and OdorCarousel, providing design guidance for future works.