In my organization we currently require that an InfoPath form be submitted and approved for the creation of a shared mailbox in Exchange Online. Even with Office 365 groups, we still have need to create traditional shared mailboxes. This requires a complicated infopath aproval process and then manual work for the creation. I think it would be quite handy and a time saver to be able to automate this process with Flow and Forms, however this does not currently appear to be possible.
Please consider adding create Shared Mailbox as one of the Azure AD or Office 365 categories.