It seems that string above is wrong I was able to do this initially but no longer
I've been through quite a few options, and this Chrome extension seems pretty solid and works automatically, without needing to be triggered:
(I found this macro in my "Translate" group too so it must be one of the standard macros shipped with Keyboard Maestro...). After the slash at end of the Google URL you are missing this path:
?hl=en&tab=TT#view=home&op=translate&sl=auto&tl=en&text=%Variable%Parameter%
Testing... 
Yep! 