Thanks for contacting Syncfusion support.
We have checked your query and would like to let you know that the sidebar component does not contain the IsOpenChanged event. Also, we suspect that your requirement is to trigger an event for opening and closing of sidebar component. If this your requirement, then you can make use of onOpen() and onClose() event of the component which will be triggered on open and close of the sidebar respectively. For your reference, we have prepared a sample.
If we misunderstand your requirement, can you please share the additional details regarding your requirement it will helpful for us to resolve your issue at earlier.
Please let us know, if you have any concerns.