Hi,
The fields in the work object in ORCID can not be customized. ORCID's goal it to make links between researchers and their outputs so we focus on having resolvable identifiers for works rather than having a schema that has fields that can capture all work metadata. (Though there is the citation field, which can hold information about the work that doesn't fit elsewhere).
Our recommended workflow for getting full and complete work metadata is to request it directly from the source, rather than relying on what was entered on an ORCID record. With this workflow you would read an ORCID record to get a list of works with identifiers for each, you would then resolve those identifiers from the source who issued them (such as using the Crossref API for DOIs, or the PubMed API for PMIDs/PMCs). Those sources will have the complete metadata for the works.
Best,
-Catalina