Your "specification" suggests that a mail merge would be most suitable. There is a Thunderbird addon that does this.

You can send using a Mailing List and Bcc:, which will (should!) hide addresses, but it also hides all the individual addresses. The message arrives showing whatever was in the To: or Cc: fields, or "undisclosed recipients;" if they were left empty. So a Mailing List isn't going to satisfy your requirement.

You have to change the To: label in front of the address into Bcc: (Blind Carbon copy). This hides the address for the other recipients. You should do this for all recipients you want hidden.

If you first change To: into Bcc: and add the first address and then add another address, Thunderbird has remembered that your previous address was a Bcc:-address and add the next ones also as Bcc:.

You can also use the Contacts Sidebar (press F9 in the Compose window), select the addresses you want to mail there and click the Add to Bcc:-button.

"…each individual address to show for the appropriate recipient…" - Bcc can't do this. :-(

Thank y'all! Appreciate your confirming that Thunderbird is a limited email program, so I shall look elsewhere. Again, thanks.

Well no. This is an example of an XY problem. You want to do X (send personalized email messages) and you have decided that Y (Mailing Lists) are the solution to your problem, so in order to do X you asked how to do Y.

The solution to X is in this case a Mail Merge. There is an addon to do this. So yes, Thunderbird can do this.

I believe there are email programs which incorporate mail merge as a built in function rather than doing it via a supplementary addon, but you may fail to discover such a feature if you continue looking for it as a function of a Mailing List, rather than embracing the concept of Mail Merge.

https://addons.mozilla.org/en-GB/thunderbird/addon/mail-merge/

You can use a Mailing List to manage your batches, but you'll need another addon to explode the Mailing List to expose its member Contacts. A Mailing List is inherently unsuited to Mail Merge because its job is to hide addressees whereas you need them to be accessible.