Add custom menu action to Caja file manager

There should be a tool to create such actions in Caja (default file manager in Mate desktop environment), installed with sudo apt install caja-actions But it doesn't seem to work, as indicated here . In my case, this tool is in the start menu, but it doesn't launch (Mint Mate 18.3, based on Ubuntu 16.04). How to create such actions manually? --- This is posted in order to provide an answer.