Creating a Chrome OS app shortcut
Follow the guide found here: Quick tip: Make a chrome app shortcut for any web app
In step 1: I created the folder in the downloaded files folder by pressing ctrl-E since I found no other place on my chromebook...
In step 3: I got an icon from this forum topic The many logos of Domoticz and resized it to 128x128 pixels. This is my version:
Good luck!