To do Alt + M D on Mac in Excel, download and install Accelerator Keys, then press Option, followed by M, D.
Command: Trace Dependents
This is how to do Alt + M D on Mac in Excel with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with Excel.
Alt + M D trace Dependents shows arrows to cells that depend on the selected cell. This helps you understand which formulas will be affected if you change a value.