Hey guys. I don’t found information about opportunity to invoke tasks from triggers. Anyway I got error in logs: Unhandled error: {"message":"invalid function format"}
Hey @gert.vali, May I get the way that you’re using to invoke the external function?
Normally need to use the context.invokeFunction which first parameter is a string with the name of the function that you want to invoke and the second one is the arguments like data or headers (you can use the FunctionEvent as guide 
) and finally the third one is some options to skip the permissions or wait for a response (optional if you don’t want to get a response or just want to execute something in background).
Hope this could be useful, let me know if you got more comments 
Further to @andres.celis, please find some info on invokeFunction here Custom Functions | 8base Docs
Sorry guys, I just forgot to export this function.