For collections, the video player has two main layouts, Sidebar and Thumbnails.
Navigate to Customization > Customize and scroll down to the Playlist position. You can choose between Sidebar or Below player (thumbnails). Select your preferred view and click Save.
The two options will look like this:
Within the Thumbnail view, there are two different layouts. If you haven't added dividers within your videos, then all of the videos will display like the first example; however, if you have added dividers, the videos will be organized under each divider and will appear as the second example.