How to change the default setting of 9600 to 115200 for Serial Monitor?

While learning more about coding, most of the sketches I study use Serial.begin(9600). But I gather that my Arduino UNO R3 is capable of 115200 and my code works fine whenever I set that manually.

So how do I permanently change the default setting of 9600 to 115200 when I open the Serial Monitor window please, instead of having to do that using the drop-down list each time?

If you set the baud rate to 115200 in the Serial monitor then next time you open it that should be the baud rate. If you are not seeing that behaviour then please provide details of your IDE version and Operating system

Yes, thanks, I am getting that repeat, so that's a fine solution. (Just have to set it manually on the first occasion in a new session.)

An associated point: I'm now frequently getting the line duplicated when I open the Serial Monitor for the first time after upload. For example, with this code in the setup section

void setup()
{
  Serial.begin(115000);
  Serial.println("sketch 04-04");
  pinMode(ledPin, OUTPUT);
}

I'm getting this:

11:40:52.415 -> sketch 04-04sketch 04-04

If I upload the sketch again (with the Serial Monitor left open) it's displayed correctly.

BTW, can I include code that will open the Serial Monitor automatically, rather than clicking the 'Send' icon?

Just have to set it manually on the first occasion in a new session

That should not be necessary. All of the IDE versions that I have used (currently on 1.8.10) kept the same baud rate when closed and opened again. Which version are you using ?

If you look in preferences.txt, accessible via File>Preferences, you should see the baud rate that is used. If you edit the file do so when all instances of the IDE are closed

There is sometimes data, or junk, in the Serial buffer on startup

You cannot open the Serial monitor automatically. It requires manual action

Thanks, understood.