Once an octane object is created with or without a header, there isn't a way to use the same object to make a request with a different header. To make the request, a new octane object would need to be made with a different header and the same credentials. It would be nice if the requests could be made with the same octane object.

E.G.
An octane object was created without a header. A get request needs to be made with the tech preview header and a put request needs to be made using a legacy header. Instead of creating 3 different octane objects, have the 2 requests be made with the original octane object and a custom header:
octane.entityList(...).get().withHeader("ALM-OCTANE-TECH-PREVIEW","true").execute()
and
octane.entityList(...).update().withHeader("LegacyHeaderName","LegacyHeaderValue").entities(...).execute()
or give a map with headers which completely replaces the old ones for the current request.