Many H&T units - identify which is which?

[Bartosz]

I bought many BLU H&T units. While adding them to the app, I lost control over which is which. Is there any way to recognize the device by a serial number or some other ID? I found no numbers or codes anywhere on the case or under the battery.

[Heinz]

When adding multiple Shelly devices during the inclusion process, I press the button on the device twice (or a few times). This triggers a small icon to appear next to the device in the app, indicating which device has been activated.

that's the only method I was able to use that helped me out