Where can I find the Claravox editor - Windows version?

I could ask them for a repair under warranty, or even for a refund, saying that the instrument is not functional anymore because of the discontinued software!

Just did it. Fingers crossed...

 I see this as being very closely related to the ominous trend where companies are cutting off access to digital products that consumers have paid for. 

Reminded me of this video, maybe someone affected by the Moog Claravox software issue could also report that in the comments, or make their own video about it?
I'm still glad that 3 1/2 years ago, when I saw the first reviews of the production model and I already started to foresee problems like this, based on the frustrating experiences I had around the Theremini's PSU causing irritating noise/warble and could cancel my CVox order with Thomann. And that was even before news about InMusic acquiring Moog Music surfaced.

I could ask them for a repair under warranty, or even for a refund, saying that the instrument is not functional anymore because of the discontinued software!

Just did it. Fingers crossed...

I don't blame you one bit. If I still had mine it's somewhere between likely and certain that I'd be looking to do the same.

Reminded me of this video, maybe someone affected by the Moog Claravox software issue could also report that in the comments, or make their own video about it?

As you suggested I just added to the comments for the video.  It seems somewhat appropriate for the subject matter, even though the Claravox cost is probably pretty small compared to what some other obsolete high-end gear cost originally.