Changing ownership of Named Credentials is quick and easy. I’d created a Named Credential under my own OEM account and decided to share it with SYSMAN so we could set it as the Preferred Credential for a certain class of targets across the enterprise.
While logged in as the current owner, traverse down through Setup | Security | Named Credentials to this screen:
Highlight the Named Credential and press the Manage Access button to bring up this screen:
Press the Change button to bring a Search and Select page:
Press the Change button and you’re done!