I have set up a custom Password Reset policy in Azure AD B2C that allows the user to change their password while displaying custom branding elements depending on specific scenarios. This policy contains a step where the user verifies their Email Address by entering a verification code that is sent to their inbox.
From this post in the Microsoft Azure Feedback Forums: fully-customizable-verification-emails
It seems it is not possible to fully customise verification emails.
However, is it possible to perform some basic customisation of the verification e-mail within a custom policy? (text sent in the "From" and "Title" sections of the email and modifications to the text sent in the body).
Currently, you aren't able to customize the email messages, but -- as you have found on the feedback forum -- this is being considered by the product team.