Thanks for your response Old_Grey. Much appreciated.
According to Fritzing's instructions, "Jumpers are connections that need to be soldered with external wires. These are shown as blue connections while traces are shown as orange ones."
I want to turn some of my orange and yellow traces into these blue wires. My understanding of Fritzing's tutorial and Simon Monk's instructions in his fritzing book is that you can right-click on either the trace or rat's nest line and there should be an option to turn that selection into a blue Jumper wire. Meaning, no trace is actually placed on your design. But Fritzing knows you intend to create that electrical connection in the real world and gives you the blue jumper as a cue in your design that that's what you're doing.
This is what Fritzing's tutorial image shows, but I can't recreate. 
I suppose I could just not put a trace there at all, and Fritzing will export Gerbers that my mill will cut the same way as if I had gotten the blue lines in Fritzing. But I'd ideally like my design to be correct in Fritzing so I (a) have a record of what I"m doing and (b) in case I ever design something worthy of sharing with others.
Or maybe I'm misunderstanding something about the process. Thanks again to anyone with help. I feel like I am probably making a beginner's mistake, or maybe a recent software update changed the UI.