To do Alt + H L T M on Mac in Excel, download and install Accelerator Keys, then press Option, followed by H, L, T, m.
Command: Format Top/Bottom More Rules
This is how to do Alt + H L T 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 L T M opens the New Formatting Rule dialog for creating custom top/bottom rules with specific thresholds.