Thank you for your post.
You aren't able to currently add components to the Component Tool, however, if you follow the steps below you can achieve a similar result.
1. Draw the desired component, with the correct size & materials, in a new SketchUp model.
2. Select the component then use the PlusSpec BIM Tool to add the product info so it will appear in the takeoff.
3. Save the SketchUp file in a folder on your computer. Note: If you save it to a shared drive, anyone who has access to that drive can also use the component.
Would you be able to please let me know if this works for you?