Channels allow you to have all lines of text matching a given pattern get directed to another window, so that you can do things like directing all output from your puppets to individual windows for each puppet.
To create a new channel:
Click on the "+" button. A new entry will appear in the list of channels.
Double-click on the line of the new entry. The area will turn into a text entry field; type the name for this channel.
In the Catch Expression text area, type the pattern you want Cantrip to use to determine which lines to pull into the channel's window. If you check the Use advanced matching, Cantrip will use regular expression matching; otherwise, it will match the literal text. The Match whole line checkbox does not currently have any effect? [Editor's note: At least it doesn't seem to do anything when I have it checked or unchecked...]
Type the name for the channel's window in the Window Name field.
Set the transparency for the channel's window using the Transparency slider. If you change this while the window is open, the new transparency value won't show until the next line of text appears in the window.
If you want the channel window to show up when you open the world file, instead of when the first text for that window comes across, check the Display on launch checkbox.
To delete a channel, select it in the list, and click the "-" button. To turn it off temporarily, uncheck the checkbox for that channel.