All buttons on the main calculator and on the 4-function calculator can be rearranged. To do so, press and hold the option key while clicking the button you wish to move. Now drag to the new location. The button you dragged to will swap positions with the button initially selected. If you change your mind before releasing the button, just drag the button to the face of the calculator so that no buttons are hilited, and release the button.
NOTE: Although you can change the button layout whether CalcWorks is registered or not, your settings are not saved between sessions in the unregistered version, so all changes are lost when you quit CalcWorks. You must register to enable saving of custom button layouts.