It's not possible to condense your separate Linked Accounts into one account that uses multiple white label profiles. Similarly, it's not possible to separate an account using multiple white label profiles into distinct Linked Accounts.
If you do need to condense multiple linked accounts into a single account that uses multiple white label profiles, the process is as follows:
Bulk export the campaign data from each individual campaign across all linked accounts that you'd like to merge (this is only available to your account admin).
Create accounts with the same names/URLs in the main account where you'd like to employ multi-profile white labeling.
Import the campaign data file from step one into each new campaign from step two (this is only available to your account admin).
If desired, cancel the subscription on the Linked Accounts.