How to find connections

None of the Chinese rail schedule sites seem capable of providing/recommending routes requiring connections (I.e. if there’s not a direct train between X and Y, they say ‘no trains available’ rather than ‘X to Z, Z to Y’ as they would in the UK.

Is there a site you’re aware of which can do this, or is it just a case of working it out yourself and booking individual tickets?

I’m looking at going from Beijing-Kashgar next spring, which is possible via Xi’an but this booking site seems to know this!

Thank you!