Though I am not quite sure what you mean by “an video streaming channel with multiple ‘channels’.”, you cannot control the Plex environment from a channel plugins. Are you wanting some shortcut key to switch between between directory items of a channel from the within the play screen?
All you do in a Plex channel is create directories to organize the media and pull the metadata to populate the media listings in each directory. Then you create media containers (usually in a URL service) that contain all the data about each video stream you want Plex to play.
Each Plex player app controls the environment. Plex channels just create an XML document for each directory with all the metadata. Each Plex player app is programmed to read that XML and display the channel directories and determine how to play the media based on the details shown in the media container. Any remote control/keyboard options in channels are part of and controlled by the Plex player app.
If you want to see the channel XML your Plex player app is accessing, the channels XML is at http://localhost:32400/channels/all?X-Plex-Token=your plex token. And then each directory listed can be accessed with http://localhost:32400/key value?X-Plex-Token=your plex token
If you want to see the media container XML and it has a URL service, the XML for it is at http://localhost:32400/system/services/url/lookup?url=the URL of the media?X-Plex-Token=your plex token
Ultimately, you would need to refer to the section of the forum for the Plex player app you are using and see if they offer any keyboard options that can be used within in channels.
