Hi and thanks for your question.
The public API is somewhat limited in scope so that it's easier to maintain backwards compatibility and easier to use/harder to shoot yourself in the foot.
What you can to is to use the setTag method to add the url as a tag to the transaction. That won't show it in the exact same spot but at least you could see it in the tags tab of the UI.
However, I agree that at least there should be a
setResult method for transactions.
If you want to build a deeper and more sophisticated framework integration including auto-instrumentation you can have a look at the contributing instructions. By doing that, you have full access to the internal API.
I hope that helps