Unfortunately there never has been to my knowledge.
You may wish to make the suggestion so a future version can have it. (Link is in my sig)
Helpful and Handy Links
Rick is of course correct that you cannot change the default behaviour of how RoboHelp creates an external link but I am wondering if that is what you meant. Were you simply asking not so much how the link is created when the URL is added but can you do anything so that when the user clicks the link, it defaults to opening in a new page?
If so, yes you can. Set the dropdown shown to New Window when you create the link.
See www.grainge.org for RoboHelp and Authoring tips
Rick was correct. I'm single-sourcing documents from FrameMaker that contain dozens of external links, and I don't want to have to change each one individually.
I don't see anything in the FM help that allows you to control this from the FM end of things, but what about editing the html code in RH? I think using the target="_blank" command will force it to behave differently.