Open a new document window starting from box File > New Data Sheet > Start from Box.

Enter the box dimension 400x400x800 mm in the left cells, then click on Add Box to add it to the list. To save time, only enable Width as Dimension Allowed Vertical to Pallet.

Change the pallet type to Europallet 1200x800 mm on the Pallet Dimensions menu.

Use the Recalculate option from the Tools menu to see the results, you will see a list of three pallets, the first two are regularly oriented and the third is calculated based on the restrictions while optimizing as much as possible the available space. Please note that the case placement restriction didn't affect the first two pallets.

Select the third pallet and then go to Tools > Layer Editor. There you are going to see the top-down view of the first layer.

Grab the first box from left to right, move it out from each other so it can rotate using the Rotate 90° in Z axis button. Repeat this step with the middle box.

This is how the pallet layer should look after finishing the rearrangement. To move the boxes you can drag and drop them or you can type the coordinates on the Position chart.

While you keep the shift key pressed and go over the Copy Selected Layer button with the mouse you should see the Alternate Layer option, click on it.

Select Show Full Pallets and do right click on the drawing and use the Toggle Pallet View option to see the new arrangement. Save your work pressing the OK button. Then you can the get a pallet report using Window > Detailed Report.