I copied the symbol library file for a 2N3904 transistor into my own library file. The statement at the top of the open symbol states “Symbol 2N3904 is a derived symbol. Symbol graphics will not be editable”. But that is exactly what I want to do. I want to change the graphic symbol to the proper IEC 60617 symbol. I have already changed the graphic symbol on another transistor and so what I want to do is copy that graphic symbol (only) over to my 2N3904 transistor so all other information is not changed. However, it doesn’t look like that can be done, must manipulate the graphic symbol in my 2N3904 library file. What do I need to do?
Copy the base symbol and modify that.
What version are you running? I think in recent versions it will copy the base symbol as well but maybe I remembered wrong.
Open the properties of your 2N3904 to see the original symbol. Use the original to make the modifications.
I am running KiCad version 9 on my desktop PC with Ubuntu 22.04 OS. Thank you for your reply. I accomplished what I needed.
It would be really great if one could just “remove” that “derived from” property. I also stumbled across this and cannot see a reason why this should not be a useful feature.
Been there a few times where I already copied a symbol to a private lib and then recognised that what i copied was derived and then starting over again searching for the “root symbol”.
Is there some specific reason why there is not a selection in a dropdown “derived from” that the user can set to “empty” to declare the symbol as not derived? 
Feel free to submit an issue to implement promoting a derived symbol to a base symbol, if hasn’t already been done.
In the mean time . . . this might help: