What I mean is when you are coding and you want to include a call to a function for instance like
NAMESPACE1::NAMESPACE2::NAMESPACE3::DoStuffWithMyReallyDescriptivelyNamedSubroutine(x.y,z);
right now I have to type that all in. Sure, Slickedit may or may not help me by suggesting name completions while I type but in many cases the parsing of Slickedit fails and it simply does not suggest anything, especially in complicated project setups with many levels of name spaces. In that case I have to type it all in or, like you said, navigate to the source code where my function is defined through the file dialog pane, if I remember where in the deep directory structure the source file is, and then doubleclick on the funciton name in the Defs pane to get there, then mark the name, copy, move to my code window and insert, not to mention I have to restore the namespace prefixes.
I can't remember what I was using 15 years ago in that company I was working but I remember all you had to do was click on a function name in the symbol browser, drag it into your code and the complete function name including namespace decoration would show up