I noticed a problem:
When a sub flow doesn't have return node, the generation is failed with error message: "There were problems generating 1 source code... Make sure all markers .... Check error log..."
But, there is no any error marker, and there is no any error in error log.

I spent an hour to find what caused this error:
Actually i created a sub flow and its last step was a form which throws an event, and since there was no error marker, i thought it can work. When i tried to generate, i received the above error.
So, it would be good to have an error marker when sub flow has no return node.

I was able to reproduce that. I will enter an MR on it. Thanks.