7.34. Add Alpha Channel
Add Alpha Channel: An alpha channel is automatically added into the Channel Dialog as soon as you add a second layer to your image. It represents the transparency of the image. If your image has only one layer, this background layer has no Alpha channel. In this case, you can Add an Alpha channel with this command.
7.34.1. Activate the Command
You can access this command from the image menubar through Layer → Transparency → Add Alpha Channel.
In addition, at the Layer Dialog, you can access it through Add Alpha Channel of its context pop-up menu.