Dominik

It can be quite difficult to change the docking once you have added the
panels to a form!

It may be easier to have all three panels on the form, docked to the
right, then just change the width of the panel you want to show/hide
(you can do this in a loop if you want it to 'grow' or 'shrink').

To change the docking order and add a panel I would:

1: Change the properties of the left panel to no docking
2: Change the properties of the right panel to no docking
3: Add the third panel (if you haven't already)
4: Select the right most panel, select Format | Order | Bring to Front
5: Change the docking to right
6: Select the middle panel, select Format | Order | Bring to Front
7: Change the docking to right
8: Select the left panel, select Format | Order | Bring to Front
9: Change the docking to right

Now you can achieve what you want by changing the width of the panel
you want to slide in and out.

There is an add on called control outline which makes things easier and
which will be built in to the next version.