A folder or file in the form /docs/[...slug] will match all segments in that position (e.g., /docs/anything/here will be matched by [...slug]).

Create a app/coures/[courseId]/[...courses]/page.tsx

export default async function({params}:{params:Promise<{courseId:String,courses:String[]}>}){
    const resolvedParams = await params;
    const courseID = resolvedParams.courseId;
    const courses = resolvedParams.courses;

    return(
        <div>
            <div>{courseID}</div>
            <div>{JSON.stringify(courses)}</div>
        </div>
    )
} 

Use case - Recursive folders. For example

https://app.100xdevs.com/courses/3/1

https://app.100xdevs.com/courses/3/1/4