Although it is not necessary, it is possible to create an icon. If you decide to do this, consider using a separate GeoGebra Worksheet to create a suitable image and then use screen capturing software such as Jing (free) or SnagIt (commercial) to create an image file. Then press the Icon button and navigate to the image file and press Open. Press the Finish button and you now have a tool for creating lines in the Poincaré disk model.