For some tasks it is required to "chain" playlists. Using chained playlists is a guarantee that there is no gap between two playlists.
Whenever a new playlist is created via drag and drop or when a previously saved playlist is dragged from the library's "Playlists" tab to the calendar view and thus placed in the schedule, the playlist is automatically set to be a timed playlist (even if the saved playlist was a chained playlist). This is because placing a playlist in the schedule means specifying a start time which is an attribute of a timed playlist. You can change the playlist type to chained but this may mean that the playlist's start time is changed depending on the end time of the previous playlist (= the playlist's start time is changed so that the start time matches the end time of the playlist before).
Timed playlist: This kind of playlist has a predefined position and is able to attach chained playlists.
Chained Playlists: The playlist starts whenever the playlist before ends and therefore another playlist has to be scheduled right before this playlist. If the end time of the playlist before changes, the start time of the chained playlist will adjust so that there is no gap between the two playlists.
Playlist Type: Select the playlist type in the inspector.