If the model number of you tv is correct, it the pip toggle command should be in there. If not you'll have to add it via 'edit IR language' for that device.

Once the harmony knows the code. Goto to MyActivities, Add Activity, Change Button Function, and follow the prompts.

You'll be asked what button, under what activity, and submenu (if applicable) you want to map. What device you want to send to, and what you want to send.

Of course you'll have to give up something. Zap most likely.