Thank you very much for this, @sandman7920! I haven't had the chance to review this in detail yet. But two general thoughts from my side:

1. Ideally we would override the vertical scrollbar behaviour and only show a window of e.g. 1,000,000 rows at a time and then move that window when using the scrollbar. This way the user could see all rows. The downside is that this makes the code even more complex than it already is and that it would somewhat break the search function (Ctrl+F). So in my opinion your solution is what we should aim for at the moment.
2. 👍 for not adding this to the Preferences dialog. But I was wondering whether we could even calculate the maximum number of rows like from the size of an int and the default (or the actual?) row height to show as many rows as possible. Not sure if it's worth the effort though.

But I was wondering whether we could even calculate the maximum number of rows like from the size of an int and the default (or the actual?) row height to show as many rows as possible

Yes, we could, but if the user resizes only one row, we are in the same position.

Another possible trigger for this issue is:

Maybe we should do something like:

tableView.verticalHeader()->setMaximumSectionSize(0x7fffffff / rows_limit);

Yes, something like that makes sense too.

Let's merge this. Nobody objected after more days than I initially thought were going to pass. 😄 Sorry for the long delay.