Hi and thank you for your question.
This can be a frustrating problem to deal with and attempt to resolve. The good news is, this is not something that is uncommon to show up in a dealership under the exact same conditions you have experienced and described.
I do not know what you mean when you say a copper cog. To me a cog is another word for a gear. At this point however, I do not think that is relative.
Having stated what I did above, allow me to say I am not here to argue with you or anything else negative. The facts we have is your clutch is dragging and nothing you have done so far has fixed it. That leaves us some options here.
Honestly, my gut instinct is you still have air in the clutch line. I fully understand you have bled it 3x. My question for you is do you have a straight shot up from the line to the master cylinder. If there is a high spot in the line, perhaps the extra length that allows the forks to fully extend, air can be trapped in the high spot in the line. You can unbolt the master cylinder from the handle bars and hold it above the high spot and pump the lever. Another trick you can use is tap on the line to create vibrations in it to help dislodge any stuck air bubbles in the line too. Use the plastic handle of a screw driver or wooden hammer handle to tap lightly on the line. Remember you are only interested in creating vibrations in the line, you are not driving nails. :)
One other trick along the same lines of using vibrations to dislodge air bubbles is to allow the spring for the lever to let it snap back when you release it. Squeeze it in like normal but when you let it go, let it go completely all at once. Similar maybe to the same idea of side stepping a clutch in a car where you just let your foot come off one side and let the pedal fly back on its own. That snapping action helps tremendously too.
I am sure you noticed that KTM sells a syringe for clutch bleeding. The reason they do that is to bottom fill it and pump brake fluid up from the bottom to fill the master cylinder, with the idea of pushing all the air out as the fluid fills from the bottom up. It is fair to say there are many ways to bleed a hydraulic system, but the goal is all the same. You have to get all the air out one way or the other.
As a test here, you can unbolt the slave cylinder from the cases, leaving the hydraulic line attached, and with necessary precautions such as a rag over the back side of the slave, hold the piston compressed with a pair of channel locks and then squeeze the lever. Observe how far the piston wants to move. Understand the idea of the pliers is not to prevent its movement or test the strength or power of the slave, just to be able to measure movement and compress the piston again when the lever is released. Light to moderate pressure on the channel locks should be sufficient. KTM doesn't give a spec for movement but it should move at least 3mm or so.
If you are getting sufficient travel out of the slave, the next thing to check is the clutch pack itself. You will want to take it apart and inspect the clutch discs (not the fiber plates) for warpage and also the outer pressure place or what KTM calls the pressure cap.
I am attaching a link to a diagram of your clutch assembly so you can see what I am talking about and also so you can let me know which piece is that copper cog you referred to.
The intermediate discs I was referring to when talking about checking for warpage are numbers 5 and 6 on the diagram. Please find that cog you talked about and let me know what number it is.