To do Alt + H A M on Mac in Excel, download and install Accelerator Keys, then press Option, followed by H, A, M.
Command: Align Middle
This is how to do Alt + H A M 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 + H A M vertically centers cell contents in the middle of the cell. This is useful for taller cells where you want content centered vertically.