To do Alt + M N on Mac in Excel, download and install Accelerator Keys, then press Option, followed by M, N.
Command: Name Manager
This is how to do Alt + M N 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 + M n opens the Name Manager dialog in Excel. This dialog lets you view, create, edit, Delete named ranges and named constants in your workbook. Named ranges make formulas easier to read and maintain by replacing cell references with descriptive names.