Why I am not able to see Test cases in Assistant?

This is expected behavior. You should see the test cases in the Folder → Testing.

If you are publishing a Process to Orchestrator (not a Test Automation) and then you are adding the process to the Folder in the Automations section, you will be able to see it under the Assistant.

Example of a published Process as a Test case (not a Test Automation process).

References:

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