Dear Altran,

If you want to make a panel collapsible, just set the CanCollapse property of that panel to Both, then a collapse/expand button will be displayed on the associated splitter bar whenever appropriate.  When a panel is collapsed, the adjacent panel is expanded accordingly.

Please see More Panel Properties in the documentation for more details, and check out Panel Properties in the demo for collapsible panels in action.

If you want to listen to the panel collapse/expand events and act on them accordingly, you may add a client-side event-handler (in JavaScript).  ZeeControls will call this handler whenever the states of panels within a web splitter container are changed.

Please see Event Handling in the documentation for more details, and check out the Client and Server-Side Events demo.

We hope this could answer your question.