Serial Monitor scrolls with Autoscroll disabled once buffer is full

[Defragster]

Describe the problem

Ide 2 SerialMonitor window keeps up but won't stop scrolling when 'Autoscroll' is disabled.

To reproduce

On Windows 10 machine: Run this sketch https://github.com/PaulStoffregen/USB-Serial-Print-Speed-Test

On a Teensy 4.0, 4.1, Sparkfun MicroMod - (or other) USB device with 480 Mbps connect and fast Serial.print() output : 500,000 lines of 32 bytes/second

Expected behavior

Output window appears to keep up without garbage or error content.

Clicking Autoscroll OFF should stop streaming data and scrolling the device output for review.

Arduino IDE version

IDE 2.0 RC9

Operating system

Windows

Operating system version

Windows 10

Additional context

For Teensy: Using TeensyDuino 1.57 beta 4, or later/release pending.

Windows 10 laptop with i7 Gen 11 CPU is running at 85%+ on Arduino.exe task, but it is keeping up with incoming .prints()

(32 character) Lines are scrolling fast at ~500K reported per second.

Overall, the 8 core i7 processor is at or near 100% CPU usage.

Ref post on: https://forum.pjrc.com/threads/70698-Teensyduino-1-57-Beta-4?p=309830&viewfull=1#post309830

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Additional reports:

• https://github.com/arduino/arduino-ide/issues/1250#issuecomment-2021321498
• https://github.com/arduino/Arduino/issues/3538
• https://forum.arduino.cc/t/toggle-autoscroll/1172875

Issue checklist

• [X] I searched for previous reports in the issue tracker
• [X] I verified the problem still occurs when using the latest nightly build
• [X] My report contains all necessary details