@NM, Thanks for posting in Q&A. From your description, it seems you want to import a pfx certificate generated by third party CA. If there's any misunderstanding, feel free to let us know.
Based as I know, only some partner like DigiCert, EverTrust and KeyTalk provide supported methods or tools to import PFX certificates to Intune. Here is a link with more details:
Please confirm if we are in the supported list.
For the query in Graph Explorer, it seems you are listing the userPFXCertificates. You can try the URL in the following link to check:
Hope the above information can help.
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