Theater nerds and dramaturgs,
I'm shocked - shocked - at my inability to locate Grand Guignol scripts. I own Richard Hand and Micheal Wilson's Exeter Performance Studies books, which contain ~21 translated scripts, but have been entirely unable to find anything outside of a catalogue of plays and a couple Dover Classics translations. I've scoured Google Scholar in english and french, but have been hampered by my terrrrrrrible french and research abilities.
Are the bulk of André de Lorde's & Oscar Méténier's scripts just... gone? Is this the sort of thing that has gone undigitized, or are they simply lost to time?
You can search through the digitized collections of the Bibliotheque Nationale de France using the Gallica platform. I just completed a search for Oscar Méténier and got quite a few digitized publications here.
EDIT: I feel that it's important to make this note for researchers of plays and dramatic literature that libraries and archives are often your best sources for original manuscripts, both unpublished and published. Many are even digitized in today's world! And don't forget to check the bibliographical information that many entries include. Often, by checking that information, you can find more detailed scholarship on the work you're studying and sometimes even translations. Happy hunting!