As mensioned previously, the alpha-channels are selection saved in your document. In PSE, we can save, load, and delete selections using the "Selection" menu. E+ adds some alternative tools from the full Photoshop store.
First off, an existing selection (e.g., just loaded channel) can be instantly saved by double-clicking the "Save as Alpha-channel". A new item immediately appears in the Channels list.
For the new channels PSE automatically generates names like "Alpha 1", "Alpha 2", etc. If you prefer more descriptive names use the "Rename Alpha-channel" command (screenshot).
To load a saved selection, choose the proper alpha-channel in the Channels list, define (if necessary) the loading mode and apply the "Load Selected Channel" command. Or just double-click the alpha-channel's line in the Channels list.
At last, if don't need a savaed selection any more, you can get rid of it by using the "Delete Alpha-channel" command.