Hi,
there is no "official" way (AFAIK), but you have basically two options:
1. Extract existing Action Macro using pdm_extract utility to a text file, modify the code and import it as a new object (pdm_load -i)
2. modify the detail_macro.htmpl form to be able to modify Macro Type (type) and Macro Code (usr_string1) attributes and set Macro Type to ACT for Action Macro.
Good luck,
Jakub