This has been requested multiple times already:
December 2018: https://deckbox.org/forum/viewtopic.php?id=30513
March 2019: https://deckbox.org/forum/viewtopic.php?id=30653
November 2019: https://deckbox.org/forum/viewtopic.php?id=30984

But each time there was never any response.

Could we please add more than one Commander in the deck builder? :( The Partner mechanic has been around for a while now and appears in several official Wizards decks.

Thank you for any help.