I just stopped Thunderbird ran it as Administrator - no changes in menus, at least no Options or Preferences anywhere. What gives?

I don't have either tools>options or tools>preferences available in the menu

It's now called Tools > Settings.

I ... don't want to have to change a bunch of passwords, just want to add an entry for smtp.mail.yahoo.com

Not sure what you're up to. You don't manually add-an account password in Thunderbird. Thunderbird will prompt you for the password when it's needed, and you can tell it to remember the password for you.

Do you know if it is possible to set up two different passwords for the same SMTP server? That is what I am attempting, to avoid having to change a bunch of SMTP passwords on multiple email tools - including the Win11 default Mail tool that's a real pain in the ass to deal with since it's so brain-dead. If I delete and add back the email, will I be able to set a unique password for outgoing email, or will it force me to use the already-defined password?

I have Settings, and can view Passwords but as has been stated I cannot add a password. If I could replicate the yahoo SMTP line with a different password, then I could select it from Settings - I've already verified that. Settings does not give me access to the Password Manager, so I'm still wanting to know how I do that with no Options or Preferences selections and it not being under Settings.

If I could replicate the yahoo SMTP line with a different password, then I could select it from Settings

I still have no idea what you're talking about. In any case, you cannot set account passwords in Thunderbird. You have to set a password for your email provider's server. And you'll have to do that on the server, not within Thunderbird. Typically there is only one account password for both, the incoming, and outgoing server. Whether this is any different for your email provider, you'll have to check with them. Yahoo certainly isn't one of them. As said before, you can only tell Thunderbird to remember the password, so that you don't have to type it again and again.

When I set up these emails at least 20 years ago, nothing told me I should use one common password for the outgoing SMTP mail server. I used the same password for sending and receiving email, which if I recall correctly was the easiest way to set up the email - so the tool encouraged doing this. Now I have three emails on 3 computers and a phone, multiple email tools on some of them, that I would have to change passwords on - and as I said, some of these email tools are a pain in the ass.

All the other apps are perfectly happy to have multiple passwords for the mail server, by the way.

Do you know if it is possible to set up two different passwords for the same SMTP server?

If you use two different SMTP server entries on the account settings > Outgoing servers (SMTP) AND Your second entry uses a unique name in the list. (You can not have two SMTP Yahoo for instance) and a unique user name.

That's precisely what I want to do . Now, is there any way to do this other than deleting the existing email and re-entering it? Is there any other way to get this entry into the list? If I re-enter it, will Thunderbird allow me to create that entry or will it 'know better' and not allow two different passwords for the same SMTP server? I actually have a third email on the same server, I can add it to Thunderbird and see if it allows a different password.

You can go to account settings and on Outbound SMTP servers pane you can click 'add' and create the new smtp server with a unique description. Then, on the account pane, click the dropdown menu to select the appropriate smtp server.

This pop-up does not let me define a password, so it does not get me what I want.

To sort this out, you need to have two SMTP servers, one for each account. For the recently added SMTP server, you will need to set the second YAHOO account to point to it, such that each YAHOO account points to separate SMTP servers. Once you have that setup done, then send email from each and report any error messages.