Final answer:
User1 should navigate to the Draft Articles view to modify a knowledge base article that has not yet been submitted for approval or completed.
Step-by-step explanation:
If User1 has created a knowledge base article and no other action has been taken, the article will typically be found in the Draft Articles view. This is where articles that are not yet completed or have not been submitted for approval are stored. As such, User1 should navigate to the Draft Articles view in order to modify the article.