from https://hl7.org/fhir/datatypes.html#codesystem
> If the 'display' element is populated, the string used in display SHALL be one of the display strings defined for that code by the code system (code systems may define multiple display strings for a single code). If one of the available display strings is labeled as preferred, it SHOULD be used.

However, CodeSystem.concept.display is `0..1`.

I assume it means you can use any of the "designations" for the Coding.display, but it would be nice to see that written.

Additionally, there is no "preferred" element/marker in CodeSystem.concept and so I assume that last line is referring to the conceptual CodeSystem being represented (and not to anything visible in the computable resource)?  Is it safe to assume that the string chosen for CodeSystem.concept.display is the "preferred" one?

Suggested wording:

> If the 'display' element is populated, the string used in display SHALL be one of the display strings defined for that code by the code system (code systems may define multiple display strings for a single code). When the system concepts are enumerated in a CodeSystem resource, the display value must match the CodeSystem.concept.display or one of the values from CodeSystem.concept.designation.

> If one of the available display strings is labeled as preferred, it SHOULD be used. When the system concepts are enumerated in a CodeSystem resource, the preferred value is typically represented in CodeSystem.concept.display, although the preferred value MAY be language-specific for some code systems.