Text below taken from above link (March 23)
Generate a temporary verification code for users who can’t access the identity verification method that they usually use for multi-factor authentication (MFA). Set the code's expiration for from 1 to 24 hours after you generate it. The code can be used multiple times until it expires. This option is available for all products built on the Salesforce Platform.
Temporary verification codes are valid for multi-factor authentication only. They aren’t valid for device activation. That is, when users log in from an unrecognized browser or app and we require identity verification, they can’t use a temporary code.
- From Setup, enter Users in the Quick Find box, then select Users.
- Click the name of the user who needs a temporary verification code.You can’t generate a code for an inactive user.
- Find Temporary Verification Code, then click Generate.If you don’t already have a session with a high-assurance security level, Salesforce prompts you to verify your identity.
- Set an expiration time for the code, and click Generate Code.
- Give the code to your user, then click Done.After you click Done, you can’t return to view the code again, and the code isn’t displayed anywhere in the user interface.
Your user can use the temporary verification code multiple times until it expires. Each user can have only one temporary verification code at a time. If a user forgets or loses the code before it expires, you can manually expire the old code and generate a new one. You can generate up to six codes per hour for each user.
Expire a user's temporary verification code
https://help.salesforce.com/s/articleView?id=sf.security_temp_id_verification_code_expire.htm&type=5
Each user can have only one temporary verification code at a time. If a user forgets or loses the code before it expires, you can manually expire the old code and generate a new one. You can generate up to six codes per hour for each user.
- From Setup, enter Users in the Quick Find box, then select Users.
- Click the name of the user whose temporary verification code you need to expire.
- Find Temporary Verification Code, and click Expire Now.