In FMP 19 I’m using the ‘open URL’ scrip step.
I.e.
"kmtrigger://macro=AAB1AFF8-4D14-4F93-ABDD-220AE8C94774&value=" & T01_ACCOUNTS::Name_Full
That will trigger the macro with that UUID and carry the data that is in the Name_Full field from the stated table.
Hope that helps.
I do use FMP exchanging data with KM quite regularly using AppleScript and/or the open URL command.
I can look at my AppleScript basic format tomorrow and post if you would like.
Also see:
Cheat Sheet: Using File Maker Pro (FMP) with KM and AppleScript