Yahoo 3rd Party sign in's

To continue using Yahoo email through a third party provider, i.e. eM client, I am required to change the password used to sign in at eM client. I cannot find how to get back to the password I originally used to set up the account. Have I missed something, or do I need to remove the account and set it all up again with the new password?

we support the OAuth login for Yahoo, which is the secure login that is required by Yahoo.
With OAuth you insert your password into an external browser window, ie. giving the password to Yahoo server directly, which then provides an access token for eM Client. The password never goes through nor is saved in eM Client, so there is no need to replace it.

So if you checked in Menu>accounts and cannot find any login details, then it means you already used the secure oAuth login and you do not need to create an App password for eM Client.