I continue to have no luck finding any comprehensive lists of manuscripts of Livy, while continuing to find all sorts of information about editions of and commentaries on Livy, and these of course in turn very often have some information about manuscripts, so I'm getting some of what I wanted, a little bit at a time instead of all at once as I'd like. One thing which has become very clear is the dominant position of one Arnold Drachenborch (1684-1748) among Livy scholars from the time he published his edition of Livy between 1738 and 1746, until at least a half century later. Edition after edition of the mid and late 18th century either sez something to the effect of "ex rec Drachenborchii" or "ex ed Arn Drachenborchii" on its title page, "from the recension of Drachenborch" or "from the edition of Arnold Drachenborch," or if it's not on the title page, a manual or Handbuch of Classical Studies informs you that a particular edition follows Drachenborch -- and screws Drachenborch up, or makes minor improvements on Drachenborch with the aid of manuscripts not available to him, or whatever, as the case may be. For decade after decade, it seems relatively few editions of Livy -- very few, actually -- were not essentially versions of Drachenborch's text. Drachenborch's edition, as it informs us on its title page, quotes remarks on Livy by Valla, Sabellico, Rhenanus, Geleneus, Glareanus, Sigonius, Ursinus, Sanctius, Frederick Grovonius, Fabrus, Valesius, Parisonius, Jakob Gronovius -- and others, besides the learned remarks of Drachenborch his own bad self. Iss a Ding! And for a while, it seems, Drakenborch was -- posthumously -- the Big Kahuna of Livy Studies, although today he's probably not as well known as either (Jacob) Gronovius or our own contemporary John Briscoe, who has just recently published his commentary on books 41-45. It has been well-received, like his earlier volumes on other of Livy's books, but that's about all I can tell you for sure right now, because iss a expensive Ding.