I've taken this a step further for Windows users with PowerShell.
Open PowerShell ISE.
Copy/paste this script from https://pastebin.com/RPmvWeXC
into the upper script pane. You can save the script locally, if you wish, as a .ps1.
Edit the $ffxiDir variable with the full path to your \FINAL FANTASY XI\USER directory.
Edit the $Accounts variable (in the proper order, as specified -- pay attention to the comments.
Once those steps are completed, press F5 or click the "Play" button on the script, enter your FFEra login credentials and the script will take care of the rest.
Remember -- "Main" account in this context is whichever account you want to copy all macros FROM and the "Alt" accounts are all of the alternate accounts you want to copy those TO!
Explanation: This uses your FFEra login to retrieve character data from the Character Search function on the website. It converts those ID values into their appropriate hex formats, keeps backups of the original directories for each Character you entered, and created symbolic links to your main characters macro data. You only need to update your main character macros, then re-log on your alts to refresh any updates.