I just installed Processing, version 3.3.4 on a Mac (OS 10.12.5). The Console window displays only the most recently generated line or two of text, and there is no scroll bar. For example, this program:

void setup() {
}
void draw() {
  println("In draw " + frameCount);
}

displays only the last two lines of text, regardless of how big the Console window is, and there is no scroll bar in the Console window. Doing Edit->Select All from the Console window only selects what is visible (not surprisingly).