Based on the provided tables (showing Sales team channels and Planning/Budget channels with their privacy, roles, and members), Admin1 can convert Planning into a private channel.

Admin1 having Global Administrator privileges does not grant the ability to convert a standard channel to private, because this capability does not exist in Microsoft Teams regardless of role.

Microsoft Teams does not provide a native mechanism to convert a standard channel to a private channel after creation. Even Global Administrators cannot perform this conversion because the feature simply does not exist in the Teams platform - private channels must be designated as private at the time of creation, making Admin1 unable to convert Planning into a private channel.