What are imported accounts?

imported accounts are those imported into your wallet using a separate Secret Recovery Phrase (SRP) or private key. They are not derived from your original Secret Recovery Phrase when you installed MetaMask.

For this reason, these accounts will not appear automatically when you restore your MetaMask wallet with your Secret Recovery Phrase (example: SRP 1). The data associated with SRP 1 cannot be added or extended to the imported account(s) from SRP 2. You would need to restore those accounts separately.

Just as you'd keep your SRPs securely recorded, you must keep imported accounts' private keys/SRPs safe to ensure you can recover/access them in future.

For information on how to import accounts, see here.