To add an episode to the playlist, please tap the button either on the preview page or the now playing page.

Also, please long press an episode in the Channel Info page, after it turns into grey, select others, and click the "three lines and a plus" button on the top right corner, these episodes could be added to the Playlist at a time.

To remove an episode/multiple episodes from the playlist, please long press one episode, after it turns into grey, select others, and click the "three lines and a minus" button on the top right corner.