In the Arduino IDE preferences, we can use a different editor. Can we use a different serial monitor?
I assume any Terminal Application will work.
I often use realterm.
Wasn't the question, "... opens automatically as the serial monitor from the IDE button..."? Not, "are there terminal apps...".
Yes, we can.
I meant, can we substitute another serial monitor that opens when I click on "Serial Monitor"?
Not to my knowledge.
The IDE controls the integrated aerial monitor; when you do an upload, the IDE closes the serial port used by the serial monitor so the upload can happen.
So the first step is to find a terminal program that accepts external commands so the IDE can control it. I don't know if they exist.
If they do exist, the next problem is that the IDE needs to be able to talk to it with the correct commands.