Sorry for the late reply, I always miss the notifications.
You can place an image in the header of the control and use DataTriggers with a binding to the IsExpanded property. Inside the triggers you can then define setters that change the Source property of the image based on the value of the IsExpanded property.
Hope this helps.
Katherine Hambley
.NET MAUI Mobile Web Developer
Do you have any ideas for adding a toggle icon, like an up/down arrow, which toggles when expanded/collapsed, in the header content?