Following parts were not submitted to Studio team because they are not (yet?) considered as being potential candidates for different reasons (Duplo, Flexible parts, Wearable parts, Unofficial Lego Parts, etc.)
However, you can install these parts in your own Custom Folder and use them in your models built with Studio. You can download necessary files on Studio Parts GitHub repository.
Except if specifically stated all these parts include conncectivity info so you can use it very easily in Studio.