Fisrt , I want to thank you.
I did something's that I did not do before. I traced everything back
Through the basement of house. After your last answer.
Power comes from a singel pull breaker
Runs out into a light and 2 wires out,
One contiues the lights the other to power plugs.
I have 2 light running a normal in and out to add
The next light .(these are pull chains also)
At the 3 light is where every thing happens, this light has a plug on it. (Basement light and plug combo)
What they did is power in and have power out to a light all the way in the
Front of the basement normal 12/2 wire. Another 12/2 to power more plugs and lights in the back rooms of the house.
The last run they used 12/3 in that light box
They took a red pigtail from the plug and to the 12/3 red wire, all blacks together and all whites together
The 12/3 runs back to a singel pull switch. Before everything ran in to the switch and out of the switch with 12/2 to the last light. This switch turned on all the lights at the end of the run .What they had, was red and black together pigtailed into the switch and black back out to light ,white wire nutted together,
I wanted to add a light out side. Because the basement entrance is out side.
I went to remove the light switch cover as a friend went to turn of the breaker. I just to look at what I was facing. I truned the screw and the lights turned off has soon as it moved. I turned it back and on came the light . I took the cover off
Looked at what they had done to remember (well I thought I did. )
I had to ad a juction box because there is not enough wire because of ware, for one and thought I could add the out side light power here also.
I came from the switch with white together and black in and out of switch
To the juction box. Here I wire the red and back together from 12/3 to black of 12/2 and wire nut the whites together .
I have lights but need to use pull chains and the one with the plug unscrew to shut off
Only light that comes on and off now is the last light in the line where I just changed the switch.

Can you please append pictures of what you are trying to say?