If a full disk encryption (FDE) password is forgotten, what can be incorporated to securely store the encryption key to unlock the disk?

Key escrow.

Explanation:

If a full disk encryption (FDE) password is forgotten, a key escrow can be incorporated to securely store the encryption key to unlock the disk.

A key escrow can be defined as a data security method of storing very essential cryptographic keys.

Simply stated, key escrow involves a user entrusting his or her cryptographic key to a third party for storage.

As a standard, each cryptographic key stored or kept in an escrow system are directly linked to the respective users and are encrypted in order to prevent breach, theft or unauthorized access.

Hence, the cryptographic keys kept in an escrow system are protected and would not be released to anyone other than the original user (owner).

Therefore, when a full disk encryption (FDE) password is forgotten, a key escrow if incorporated can be used to retrieve the password. Subsequently, the password would then be used to unlock or decrypt the disk.