Im not aware of a standard control that offers this functionality. There may be something in WPF or a third party control you could use.
Alternatively you can add this yourself fairly easily using a timer.
Add a tiemr to your form and in its Tick event reduce the size of your panel by a small increment. When you want the panel to shrink just start the timer and at each tick check wether the panel has "disappeared". Once it has shrunk beyond sight, disable the timer. Do the same in reverse to have it reappear.
Thanks for the answer.
I found a Collapsible Panel control on the MSDN Gallery so I'm using it.
But now I found another problem ¬¬
How to add Controls to a Panel at runtime? (so new to this...)
And sorry for making so many questions