@Alejandro Aguirre - The only way to hide your identity is to access a board as an Anonymous Guest Editor. This would involve the board being set to Anyone with the link → Can view/comment/edit mode.

You would then have to either sign out of your current Miro session or access the board via a private/incognito browser window (or install a secondary browser and always access the board from that browser while not signed in).

Once on a board as a Guest, you would show up this way in both the dashboard and on the board itself:

And if you would like the ability to hidden/stealth mode, that sounds like a cool wish list idea that could be created by following the guidelines here: Wish List: Everything You Need to Know.

Thank you very much Robert, best regards.