2024-12-05 IDE v2.3.3 and this bug is still present.
The serial monitor in the Arduino IDE is effectively broken by this lack of support for select and copy. This affects everyone using the platform and inhibits our ability to help others: no longer can I ask a novice user to run a sketch, switch to the serial monitor window and copy and paste the contents to an email or forum post.
The pushback from those here defending the lack of resolution to this issue is astounding.
Yes, experienced users can run any program they like to capture serial output. Have the Arduino devs forgotten that their core audience are new developers and students?
For those without time to read the rest of this thread. The issue is that selection of text in the serial monitor is limited to what is on screen at that time.
This has nothing to do with autoscroll.
Going to the top of the output, clicking and then scrolling to the bottom and clicking while holding shift, expecting all text to be selected, will only select the text visible on the screen.
Using CTRL+A selects text from the code window, not the terminal window (regardless of where the focus is).
The kludgy workaround is to select what is on screen, copy and paste, then scroll down and repeat.
The proper workaround is to revert to v1.8.