How can I format a facing-page (single column) diglot using XXA books?

Question

Similar to the other diglot question from 2+ years ago, I have found a surprising (to me) behaviour trying to use XXA books to format a diglot for an extract of verses from Luke in closely related languages.

Text from LUK in diglot is formatted as 2 columns (so each language is on each page), but the XXA books are included all language A then all language B.

What I would really like is the ability to have single column so language A is on left and language B on right in a booklet format, with appropriate page numbers, and as lined-up as possible (headings etc), all coming from XXA books. Is this still something I need to look for a plugin to achieve or have the many recent updates included this? I haven't found all the diglot documentation yet, so am happy to be pointed towards that.

Answer 1

Aaargh. Just lost my nice long answer.
Short version: This needs work on the UI. If you need it working immediately, then you could rename the files to some book where the UI believed it is scripture.
or you could edit the python.
or you could ignore the python user interface and merge the files either manually (NOT recommended!) or with one of the command-line tools that probably don't make it into the distribution, but are there on github (under python/scripts) - there are 2, the perl version (older) and the python version.

Documentation (mostly written ignoring the user interface, as that changes too much and should be self-documenting anyway) will help you in the last case, but there isn't a set-by-step howto.
https://github.com/sillsdev/ptx2pdf/tree/master/docs

[Edit: I've added a github issue about this: https://github.com/sillsdev/ptx2pdf/issues/988]