Some options to get those translatable strings out of your templates. I will be adding new things, as I discover them :)

  1. xgettext-templateHandlebars & Swig
  2. gettext-twig – {% trans „string here“ %}
  3. rtwix – Ruby based TWIG translations extractor
  4. twig-po – Extract translation keys from twig templates and move them to PO
  5. Twig-Gettext-Extractor –  tool which extracts translations from twig templates

Enjoy coding …