Indeed, there is a l.h. tenth at the end of the Capriccio BWV 993. However, this is not a good example because, as I have written elsewhere, this is one of the many pieces of Bach that appear to require a “single-note pedal”, an easy to make contraption, whereby the l.h. is relieved from producing the almost impossible E-e-g#. This said, some scholars have observed that young works by Bach required large hands, and therefore he most likely had large hands himself.
Needless to say, tenths for the left hand (and for the right hand) are rare in harpsichord music, but not unheard of, and indeed they are found even in published works by renowned composers, e.g. in Handel’s last of the Eight Suites, where no pedalboard is prescribed or assumed: 2nd mov. Allegro bar 136, and also in the Gigue, bars 10-11 and similar passages later.
They would still be a great addition, though. I have no skill in transposition or I’d make it.
@CDV Here I’ll expose my ignorance for all to see. Why do you transpose down a fourth from the violin sonata original?
Oops. I failed to read the original question carefully enough.
Le 05/08/2023 22:46, Claudio Di Veroli via The Jackrail écrit :
Hi Dennis, very interesting your points, but I disagree on some conclusions. Bach did wrote for non-pedalboard instruments pieces where a tenth is unavoidable. In the WTC book I, as I have noted on teh introduction to my edition, sometimes it is easier to play a tenth with the left hand than to make matters awkward for the right hand, as in some bars of Prelude 7 in E flat major BWV 852, or else in the Fugue 16 in G minor BWV 861, in different bars. In the first beat of bar 18, either you play the tenth eb’-g" with the r.h., or you play the tenth c-g" with the left hand. On the 2nd beat you have another equally challenging, although different, large-interval hurdle. In the Fugue 20 in A minor BWV 865, bar 22, 1st beat, you have a tenth for the left hand, and the r.h. cannot be of any help. In the Fugue 24 in B minor BWV 869, bar 52,1st beat, the only way to avoid an eleventh for the left hand is to either not keep the b flat quaver as written, or to play a tenth with the r.h. I should also check one of the youth Bach Capriccios where I remember having played tenths as well.
Thanks for all these examples. I think they confirm my point: in all of
them, it is more or less possible to cheat by shortening a note in one
of the voices. (I didn’t find the example in BWV 865.) Nowhere do you
have a chord in long values with a major tenth from a natural to a
sharp. I don’t claim to have played all Bach’s harpsichord music, so
perhaps someone more knowledgeable will come up with examples. In the
meantime, the only one we have is by Davitt Moroney. So I still don’t
think your final chord is something Bach himself would have written. I
only mentioned this because you wrote: “We are reconstructing how Bach
would have written a harpsichord version.”
But Claudio, here is from Wikipedia:
Music theorist, instrument maker and organ player Jakob Adlung writes (Anleitung zu der musikalischen Gelahrtheit, Erfurt, 1758), regarding the keyboard works by Bach – ”They are actually violini soli senza basso, 3 Sonatas and 3 Partitas, which are well suited for performance on the keyboard”.[7] Johann Friedrich Agricola, who co-wrote Bach’s obituary, reports that ”Their composer often played them himself on the clavichord, and added so much harmonies to them, as he found necessary”.[8]
I think it would be a great project.
I’ll buy a copy. 
Thanks Andrew again. Quite busy at present finishing other editions. Tell you what I will do next (early next year?). 1) I will put together the 2 or 3 pieces by Bach for which I have solo harpsichord transcriptions (my favourite one is the first movement of the F minor sonata for violin and harpsichord). 2) I will check Bach’s solo violin, cello and lute for suitable pieces for the harpsichord (I have a terrible keyboard edition by Howard Ferguson of a Lute Suite in c minor, no BWV number, with all sorts of crescendo-diminuendo, OMG!). If I get the feeling, I promise I will produce suitable harpsichord versions and then sent them to you for your Dorico work.
I realise now, looking at the index of Gustav Leonhardt’s transcriptions (I do not have Henstra’s edition), that he transcribed 5 of the 6 Sonatas and Partitas for solo violin, and 2 of the cello suites. I am not sure I wish to enter an open competition with Henstra’s Bärenreiter edition. . .
And again, regardless of GL’s transcription, I find quite a few of the solo violin movements ill-suited for the plucked string. A famous case is the Chaconne, transcribed for the keyboard ever since the times of the notorious “Bach-Busoni” piano version. The piece abounds in details that do not sound well on the harpsichord or clavichord, such as long passing notes, which have faded away before the ensuing note is played. The effect is clearly meant for the sustaining power of the violin bow.
Then, again, for the Fugue for lute/violin/organ, we have 3 components we lack in any other of the solo violin/cello movements: 1) I see in this particular movement, and not in many others, a clear writing meant for the fast decay of plucked strings, 2) an extant lute version, 3) an organ version from which to extract Bach-authentic keyboard fillings.
Transcribing for the keyboard other movements for solo violin entails to introduce significant changes in order to avoid the issues of the plucked string decay, plus adding the necessary filling for the keyboard, and without an authentic organ version, these changes and additions are inevitably arbitrary, as we are not in Bach’s milieu. GL surely felt he had the composition skills to produce them in Bach’s style. I do not have such a skill.
Le 06/08/2023 15:28, Claudio Di Veroli via The Jackrail écrit :
A famous case is the Chaconne, transcribed for the keyboard ever since the times of the notorious “Bach-Busoni” piano version.
Don’t forget Brahms’s version for the left hand, well before Busoni.
So for those of us with smaller hands how do we execute the D-Fsharp tenth in the final bar?
Andrew: “So for those of us with smaller hands how do we execute the D-Fsharp tenth in the final bar?”
What is wrong with playing the D an octave higher?
David
My hand is very, very small, with ridiculously short fingers. I play that tenth arpeggiato: firmly on the D, I then play the f#. After some practice, I can do it a little faster.
You’d lose the profundity and gravitas of the low D.
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Le 06/08/2023 16:35, Andrew Bernard via The Jackrail écrit :
So for those of us with smaller hands how do we execute the D-Fsharp tenth in the final bar?
Marco Mencoboni uses his nose in the final chord of a piece by Trabaci.
You could do the same here.
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I think the Chaconne makes an excellent harpsichord piece. My transcription of that will be published soon.
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As PDQ Bach says, “Only he who is running knows.” 
I deduce from the droll answers there is no good solution.
If you arpeggiate, even quickly, you lose the low D. I like he transcription but for the last chord.
I would not believe it had I not seen it! Nuts!