The CredentialStoreItem cmdlets, in their current implementation, use the DPAPI methods to encrypt/decrypt, and store the data in a local XML file.
The DPAPI is the reason these cmdlets are not supported on PS Core.
This proposal suggests providing the possibility to use any Credential Store solution to store and retrieve credentials.
This could be implemented by asking the user to provide basic CRUD functionality to access his Credential Store solution of choice. This functions could even be provided as code-block parameters on the CredentialStoreItem cmdlets.
If none are provided, the cmdlets can eventually fall back on their current solution.