If I have by example 4 columns in the group by, is it then possible to open just on level and collapse the last three level when I expand a "main" level.
The grid itself expand the number of levels, that it was before I collapse on the highest level
I'm not srure I understand your question. But you can control the expansion of any row in the grid. The Row has an Expanded property, so you can set this to true or false. You can also use the ExpandAll and CollapseAll methods.