Well first of all it is easy to make symbols using the symbol editor. You would put the edited symbol in your own personal library. (The standard library is blocked from edits, because those symbols are likely to be overwritten when you update KiCad.)
It looks like you are trying to add power pins to one of the units of a dual op amp. I usually use it that way but often it seems that others prefer a separate “unit” for power so that a dual op amp would have a total of 3 “units”.
But I can try to make it easy for you this time around. Find my libraries posted here:
and in there is my LM358 symbol.
I did not make this symbol (or this library) for anyone other than myself. Mine do not have any internal coloring…
And…the KiCad symbols you refer to are not useless. Rather the choice of whether to have a separate unit for power is more a matter of personal preference. Sort of like box resistors versus zig zag resistors. But I do think that the zig zag resistors provide better cooling. 