To do Alt + H I C on Mac in Excel, download and install Accelerator Keys, then press Option, followed by H, I, C.
Command: Insert Columns
This is how to do Alt + H I C 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 I C inserts new columns to the left of the selected columns. The number of columns inserted equals the number selected.