The R4 implementation of Procedure (Reads and Searches)[1] and AllergyIntolerance creates[2] is now available.
Please take a look at our documentation on fhir.cerner.com and our server release notes [3] if you have any questions about consuming the resources.
[1] https://fhir.cerner.com/millennium/r4/general-clinical/procedure/
[2] https://fhir.cerner.com/millennium/r4/general-clinical/allergy-intolerance/#create
[3] https://wiki.cerner.com/display/OpenDevRN/Cerner+Ignite+APIs+for+Millennium