Hello, Kenneth - welcome to the Canvas Community! Although common education nomenclature may have us referring to exams as summative assessments and quizzes as formative assessments, the term "Quizzes" in Canvas is really just referring to any assessment created using the Quiz tool (either through traditional Quizzes or new Quizzes). You can use the Quizzes tool to build out assessments however you want them, formative or summative. That part is completely up to you! If you want students to see a Canvas quiz as a Unit Exam, simply title the quiz "Unit Exam #1" or something similar.
In terms of what students see on the left-hand navigation bar, since Quizzes is the built-in tool to Canvas that's going to be what populates; unless you're using an outside testing platform for unit exams, I don't know of any way to add another navigation tab for something inside Canvas (basically, I don't think you can separate the Quiz tool into two separate tabs - one for quizzes, one for exams).
However, I've actually moved away from recommending my teachers from even showing the Quizzes tab in their navigation; instead, I have my teachers just create and place the assessment directly into the Module. From there, students only see what you title the assessment (in your case, Unit Exam) and you won't have to worry about students being confused about what they're completing. If you're new to Modules, I would encourage reading up on them here.
If you have any other questions or clarifications, please don't hesitate to ask. Thanks!
