I always like it when someone supports uibuilder
v6.1 is the next release of uibuilder and it adds a Open and Docs buttons to the top of the Editor node panel:
Not quite what you are asking for of course. But you've prompted me to add something to my backlog to look at the possibility of an action that would be available when a uibuilder node is selected that would open the web page.
Let me know if there are other conveniences you'd like to see in uibuilder.