Quick, clean, and to the point

Move active cell left in a selection

Windows shortcut 
Mac shortcut 

This shortcut will move the active cell left one cell when there are multiple cells selected.

Related videos

The videos below show how this shortcut can be used.
Setting up a running total in an Excel table is a bit tricky because it's not obvious how to use structured references. This video explores some options.
In this lesson, we cover shortcuts you can use to move the active cell in a selection.