The answer is you can't. So let me ask the next obvious question without being insulting, a challenge. Who at Google / Fitbit has decided that selling more watches is a bad thing ?
I would like to have one for exercise and rougher work and another for more civilized times. I would like all those (largely steps) to be cumulative.
Why have a Label category that doesn't accept or limits labels? Define what is acceptable.
'Looking for a product, for a company that has more sense.
