Circumvent the Harmony remote device limit with this hack (pictures)

Click "Your devices" and choose an existing device to "piggy-back" the new "phantom" device you want to add. Choose a device you know will be active (powered on) during the new activity you'll create to associate with the phantom device you're adding. I chose my Panasonic TV since I know it needs to be on to watch TV via a Roku. If you're adding an audio-only device you may want to choose your AV receiver or home theater system instead.

On the next page, choose "Add or fix command."