To do Alt + A K on Mac in Excel, download and install Accelerator Keys, then press Option, followed by A, K.
Command: Edit Links / Workbook Links
This is how to do Alt + A K 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 + A K opens the Edit Links (or Workbook Links) dialog. This shows all external links to other workbooks and allows you to update, change source, break links, or check the status of linked data. Note: This button is only active when your workbook contains external links.