Hi Kai,
Thank you for using Syncfusion products.
It is not possible to get the currentcellset while using relational data source in OlapGrid. Because while assigning relational data to the itemsource of the OlapDataManager, it directly go to the build engine without getting processed on MDX parser. Without having MDX we cannot create CellSet.
Please let us know, if you have any further concerns.
Regards,
Sabapathy.K