add secondary sort-property

[gerpres]

hi all,
in dgrid 0.3.x I used _getQueryOptions to add another - in fact primary - sorting property prior to actually query the store.
I need this, because I want to have some sort of grouping.
The user can just select one single sort criteria, and the rendering (in the header etc.) is just fine.

We recently switched to the latest dgrid+dstore - I'm having a hard time figuring out, how to build a similar system. It seems to me, that _StoreMixin.setCollection() may be a good starting-point. but the sort-array is given to the collection "as-is".

Is there any feature I'm missing?
regards