It would be very useful to have the ability to subset a dataset using bcftools expressions for regions (-r/-t), filter expressions (-i/-e), and samples (-s).

This is now possible using the work we have done in vcztools, such as sgkit-dev/vcztools#234. In particular, we now have an index that allows efficient region queries (which will address #25).

This will also address #1084.

See an initial prototype in sgkit-dev/bio2zarr#365 (comment)