Never mind, I misread the man page, that's just if you're setting identifiers/tags.
...
I have experimented, and I can get it to set the series and index like this:
Code:
calibredb set_metadata -f "series:randomness [22]" 698
but if I use the same code with #subseries instead:
Code:
calibredb set_metadata -f "#subseries:randomness [22]" 698
It doesn't affect the index at all. I think this may be a bug.