The following both worked for me:
Code:
ebook-viewer.exe --open-at toc:"chapter 2" "The Chrysalids - John Wyndham.epub"
Code:
ebook-viewer.exe --open-at epubcfi(/24/2/4[6LJU0^-ade3ad6bcd714056b39406a49aa9a0e0]/46[chr0000326]/1:360) "The Chrysalids - John Wyndham.epub"
The later I got the location - that long gobbleydegook string - from the viewer by pressing ESC, clicking "Go to" and then clicking "Location" which then displays a "Currently at .." with a copy button. Clicking copy copied the location to the clipboard.
If I was going to use this for real I'd probably want to save that somewhere - or just create a bookmark. But I can see it might have its uses. Otherwise for me, the toc version is more useful.