Hi, welcome to devnet.
Although it's somewhat nonstandard behavior, you can do something like this:
auto buttons = box.buttons();
auto it = std::find_if(buttons.begin(), buttons.end(), [&](QAbstractButton* btn){
return box.buttonRole(btn) == QMessageBox::ActionRole;
});
if(it != buttons.end())
(*it)->setText("Foo bar");
Note though that the text is set every time the button is clicked, so you might want to connect to the clicked signal of that button and change your text there.
