How to set a YouTube Video in a playlist to be displayed first
Click the Sort dropdown and make sure you select Date added (newset).
Then drag and drop the video you want to be displayed first at the top of the playlist.
How to find an existing playlist
https://support.google.com/youtube/answer/57792?co=GENIE.Platform%3DDesktop&hl=en
To find your playlists, go to the Guide and click Library.
Create a playlist
Find a video you want in the playlist.
Under the video, click Save.
Select a playlist such as Watch Later, or a playlist you've already created, or click Create new playlist . If you create a playlist, enter a playlist name.
Use the box to select your playlist's privacy setting. If it's private, only you can view the playlist.
Click Create.
Edit a playlist
Select the playlist you’d like to edit in the Guide.
Click Edit by the section you’d like to change.
Delete a playlist
Go to one of your playlists.
Click the Menu .
Select Delete playlist .
Confirm that you want to delete your playlist by selecting Delete.
Note: Your old playlist may continue to exist in viewers’ watch histories.
After you delete a playlist, the playlist URL and title will no longer be visible or searchable in YouTube Analytics. Data associated with the playlist, such as Watch time, will still be part of broader reports, but won't be attributed to the deleted playlist.
How to Create a Playlist On YouTube 2020 [New Method]
YouTube are in the process of creating a new Creator Studio for video creators and some of the basic functions have changed, one of them being how to create a playlist on youtube and add videos to them. In this simple tutorial, we show you how and an awesome way vidIQ can help you even more with playlists!
https://www.youtube.com/watch?v=LTK4PiI5VwU