If you are using tokens or if the dynamic tag simply outputs the course URL, you can append the ?tab=reviews parameter manually like this: token?tab=reviews or {{course_url}}?tab=reviews which generally works.
If that doesn’t work, let us know your exact use case and we can check a solution for you.
The tag {{course_url}} isn’t valid unless it was manually added by you. But, if you want to use the LearnDash course URL token, just add your query parameter at the end of the token. See this reference: https://share.zight.com/GGuj0zXq