Absolute reference is set to Shift+F4 (because F4 is set to Data Sources). This is quite annoying since F4 is the STANDARD key since Lotus 123…
You can change this by going to Tools, Customize, Keyboard tab.
On the Shortcut keys locate Shift+F4 and press the Delete button. Then navigate to the F4 shortcut and choose Category: Insert, Function: Relative/Absolute References and press the Modify button.
You can now set Shift+F4 to Data Source if you wish…
Don’t forget to press OK when finished!