Catalog entry - orderable

Where should be the information about the available quantity of orderable entry?

At this point, FHIR doesn’t have resources that deal with inventory management - the general thought is that this is an area that isn’t healthcare-specific. However, you’re far from the first person to have asked. For now, you’ll have to use extensions, but feel free to submit a change request if you think it’s something that should be added to the core standard.