Hi @SensorGuy, welcome to the Cayenne Community.
I see what is going on here, I just need to talk over with the our Product team how we're going to proceed.
Long story short, we have a whole slew (like 50+) of new icons basically ready to go live into Cayenne. But they shouldn't be appearing just yet. This is why they are missing from the menu, and lost when you make any change to the widget.
Technically it's a bug that they are appearing like this when you pass data through the MQTT API in the first place, but they are basically ready to go. So rather than hide what you're seeing on widget creation, I'm angling to get them 'officially' added so you can have fun with these new icons
I'll update as soon as I know more, and when that might happen.