The expand/collapse state of the groups is part of the data and controlled by the value of the field set in the expandField prop:
If all groups have to be collapsed, I can suggest to loop over the data and set the expanded field of all records to false. This is an example showcasing it:
As the groups can be nested on many levels, the example only covers the first level, but it can be done recursively to cover N number of group levels if needed.
I hope this is helpful.
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