Currently companies must be added 1 by 1 when using proxy voting. However, when a B2B organization has a large customer base it can be quite difficult/time consuming to get all those items in.
Good news. You can already import companies (called organizations) by going to Settings > Workspace. Choose 'Import from CSV' in the left menu and then choose record type 'ideas organizations'. You can learn more here.
Please let us know if you have any other ideas or feedback!