This is not a bug report, it is a feature request.
In the current documentation, Chapter 8 address lists are described.
Recently, I found that good old bib-format is also used for glossaries https://ctan.org/pkg/glossaries-extra?lang=en
I feel, also for address lists, this would be the way to go.
The address list is a document of all possible addresses, e.g. customers .
Only those addresses take memory which are really needed.
To that end, the letter class must write a file with the identifiers of the addressees running latex.
An external tool chooses the according entries in the bib file of addresses.
In the next altex run, these addresses are in the document.
Very smooth and in line with bibliography and modern glossary.
If you want, i could write the external tool.
For bibliographies it is biber or bibtex, for glossaries it is bib2gls and for letter we had to write bib2addr.
Write me if you are interested: rei3ner@arcor.de
Do you know, e.g.,
adrconv
? You can find it also in the bibliography of the KOMA-Script manual, referred in chapter 4. Unfortunately the user manual is available in German only. Maybe it would be a good idea, if someone would translate it.IMHO something like this already exists or would be a new feature, which can be implemented as a third-party package. The idea is not necessarily limited to KOMA-Script.