This page of the configuration dialog allows you to change the assignments of mouse buttons and modifier keys to the actions described in Playing on the puzzle table, Mouse interactions. Care should be taken to avoid ambiguous assignments. Three of the default assignments can go to the mouse button because the pointer is over different areas when you use them, but the other assignments must be distinct.
The interactions are divided into those that can be assigned to mouse buttons (e.g. Move viewport by dragging), and those that can be assigned to the mouse wheel (e.g. Scroll viewport horizontally).
To the right of the name of each interaction is a button with a picture of a computer mouse which shows the currently assigned action. You can configure the interaction by clicking on that button with themouse button and then with the mouse button which you wish to assign to this interaction. If you hold modifier keys while clicking for the second time, the puzzle table will allow this interaction only while these modifiers are being held.
Instead of clicking, you can also press Space to assign the special No-Button to this interaction. This is only allowed if modifier keys are being held. The No-Button means that the modifier keys take the role of the mouse button: The interaction starts when the modifier keys are pressed, and stops when one of the modifier keys is released.
This tab works similarly to the previous one. When the button on the right asks for input, you have to turn the mouse wheel instead of clicking a mouse button. Holding modifier keys is allowed, too, with the same consequences as in the previous case.
If your mouse has a bidirectional mouse wheel (as most commonly found on notebook touchpads), you can take advantage of this: The button will recognize whether you turned the mouse wheel horizontally or vertically.