That is specific to the decoder you are using. The front and rear lights have a separate + line because in that decoder, they are current limited so you cna use regualr LEDs with no resistor. The additional functions are not and will need resistors with LEDs. There's no need to try and solder 3 or 4 wires to one pad, just solder one wire, and split that wire off to each light.
I'd suggest starting with a simpler project, or wiring this up on the bench instead of trying to work int he loco so you cna test it all and verify it works. Then try stuffing it all in the loco.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
How come decoders have the +and- for the FOF,FOR and F1,F2 functions but not for F3,F4. If so does that mean that one will connect two wires to the F3 and F4 pad as opposed to one wire going to F1+ and the other goes into F1-F2 and the same for FOF and FOR.