Hello, Ofer,
I can suggest checking the following example on how to set up the expanded prop:
https://www.telerik.com/kendo-react-ui/components/layout/panelbar/controlling-state/
We also have a feature logged to make this dynamic:
https://github.com/telerik/kendo-react/issues/583
Currently, it can be dynamic as well when setting the key prop of the PannelBar to the same value of the expanded property, as this will re-initialize it when the expanded state changes.
Also, if the requirement is to make them all expanded initially, this can be done by looping over all items and setting their expanded property to true.
Regards,
Stefan
Progress Telerik
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