Well this conversation has been spread over so many topics on this forum that it’s hard to tell who told you what. But if you go back to my last post I tried to make it clear that, although most of your GND and power connections will be of power input type, there needs to be one, and only one, pin of power output type to drive them.
Another case where I don’t know why these pins would be passive but, as was explained to you already, you have two choices. Either modify the symbol so that the pins are power outputs or add a power flag to the nets near those pins.
This is another one of those poorly worded messages. You either do not have permission to write to files in that folder or the files are write protected. Either way when modifying a symbol, or footprint, from the KiCad libraries you should not be trying to save your changes back to the KiCad library. You should instead be saving these changed symbols and footprints to your own libraries in your own folders, and then add these libraries to your project. There is plenty of information on this forum on how to do that.
And as I said previously, your barrel jack is wired incorrectly. If you look at the photo you posted as well as the symbol, that big fat thing attached to pin 1 of the symbol is the center post shown in the photo. You not only want to connect to that pin but that is usually the positive pin, you need to check with the adapter you plan to use. Pins 2 and 3 form a switch. When the plug is inserted the outer sleeve of the plug makes contact with the pointy part on pin 2 and pushes it away from pin 3. So with the plug inserted you have power applied to pins 1 and 2, pin 3 is open in this case but can be used to switch to a battery for example when the plug is removed.