Prioritization is only applicable to channels with a single thread. (Slack, Teams). Admins can prioritize Enrollments in a schedule for Learners, which means the Course will be pushed to the top of a Learner's queue for single-threaded channels by enabling the toggle under the Enrollment Options for the specific Course.
How to Enable "Prioritize Enrollment" for a Course:
From your Admin Dashboard, select "Learners".
Search for the individual Learner that you want.
Click the Pencil "Edit" button.
Now you will appear in the Learners Enrollment section for the Courses that you want to prioritize.
Click the "ACTIONS" drop-down list next to the Course of choice.
Select "Prioritize".
Viola! Now the Course will become pushed to the top of a Learners queue to become next in line.
NOTE: You are only going to see the "Prioritize" option for an Enrollment in the "Up Next" status and that isn't already at the top of the queue. If an Enrollment isn't in "Up Next" or is in Up Next but already is the first one that will start after their currently active one, then it won't have "Prioritize" option.