You can remove an app from a playlist that you have created by doing the following:

1. While logged in to your Glitch account, click on your avatar which is located at the top-right corner of any page on glitch.com

2. In the popup menu, click on your avatar.  This will take you to your profile page.

3. Click on the playlist that includes the app that you want to remove.

4. In the playlist, look for the app that you want to remove.

5. To the right of the app name, click the little down arrow to reveal the options menu.

6. Click on Remove from Playlist.

Keep in mind that removing an app from a playlist does not delete the app itself.