We have added suggestions for improvements in the GitHub items.
If the current state of the Grid with grouping is unacceptable, these are the available options:
1) Comment in the issue to add the option with all items available.
2) Use the TreeList component as it has a different virtualization logic and can also wort with tree data:
3) Use the Grid without row virtualization, only with column virtualization based on the number of items. The Grid will render fast with around 500 to 1000 records.
4) Use the paging functionality of the Grid to improve the performance. The paging is working as expected with grouping.
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