I been trying to figure out how to use this feature with little success. I been putting in the source and destination points with little trouble. The problem really happens when putting in the wires going into the multi-conductor cable. If I use the regular wire tool it wants to put in a connection point.
I have only used this tool on a couple of projects and here is what I have found about how it works. You have to use the AutoCAD LINE command to begin your "wire" fan in/out geometry, up to the point where the fan in/out wires would be horizontal or vertical to connect to your device. Use the Wire Tool for completing the circuit wiring to the device.
Now insert your fan in/out Source & Destination symbols. Then use the Markers - Fan in/out - Layers Toolbutton to assign the basic geometry to the "_MULTI_Layer" layer.
This is how it has worked best for me. A lot of steps but it works. Maybe the pros with speak up and give us some clues. Hope that helped.