Hi @davide.azzali,
When trying to add the custom widget, if you see that you can’t click “Step 2: Add Widget”, see what happens if you select a different device (Rpi, SERRA AGUO, etc) and then select your Arduino Mega again. In my case, I was able to click “Add Widget”.
This might be a bug on our side, so we are investigating now…
Thanks.
-Jesse