Yes, we have an Agency subscription that will let you add up to five Twitter accounts under the same Owlead Account.
If you want to add more than five Twitter accounts, we can merge more Agency subscriptions under the same Owlead account.
The only plan available to be merged is our Agency subscription, unfortunately we can't join Starter/Medium/Pro/Unlimited subscriptions.
If you want to add more Agency subscriptions to your current Owlead account, open a ticket, and we'll arrange it for you.