Pelease dont merge this yet. Thanks.

Sorry about my last comment, but I wasn't at the computer and I couldn't explain myself. The reason I disabled the selection is that when you click the trace header to collapse/expand it, random parts of it are selected by the browser:

Is there any way to enable selecting text but disabling that undesired random selection? Thanks!

You don't need to apologize!
However, that's really weird. I tried on my own laptop, using chrome, safari and firefox, but I don't get such random selection by simply clicking on the header for collapsing (except when double-clicking, but that's the normal behavior) :/

Can someone else try on his side?

Oh, but re-considering your gif, that's indeed because you're toggling it quite fast, so it's considered a double-click by the browser.
I'd say it should not really happen in normal usage of the page. You're not likely to collapse/uncollapse everything like this. However, you're likely to need to select and copy the exception or message 😄

OK ... and have you tried collapsing/expanding each line of the trace? Because I remember having issues with that too: the entire line was selected and looked ugly.

In any case, 👍 from me if you have reviewed this and it works as expected.

I've just tried. Nothing to report. Maybe the issues you're talking about were more prominent and annoying in a first version of the redesigned page, but now the result is really satisfying to me :)
The only issue I still get by expanding everything is the one I suggested to fix in #22971. Sometime it gets entirely out of my screen.

Yes, but I thought the error reported in #22971 was fixed and merged in another PR. It was the first thing some people notice with the redesign and there was a PR for that. I can't find it now.

Thank you @ogizanagi.