You are better off asking different questions in different topics.
How are the videos ordered? Are they consistently ordered? Keyboard Maestro can know which file you initially select (Finders Selection collection), and can list folders (Folder Contents collection), so it should be possible. It depends on how you want to play the videos.
It depends on the palettes as to how they are hidden. You can use the Conceal Macro Palettes action.
Palettes are configured either in each macro group, or the Palettes preference.