To do Alt + P T H A on Mac in Excel, download and install Accelerator Keys, then press Option, followed by P, T, H, and A.
Command: Save Current Theme
This is how to do Alt + P T H A 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 + P T H A saves the current workbook’s theme as a custom theme file (.thmx). This allows you to reuse your custom combination of colors, fonts, and effects in other workbooks or share them with colleagues.