I really do love qt-creator and it is my IDE of choice for c++-development. But it has here and there some flaws....beside the fact that there are not tabs to represent the opened files, one strange thing is that outputs to stdout get are not visibile immediately. I'm not 100% sure how it is triggered (maybe when the internal buffer is filled completely?).
In order to show the output directly, just add this to your main.cpp:
setbuf(stdout, NULL);
Another flaw is that from time to time you have invalid start-configs and qt-creator refuses to start your application. This is due to the path not set properly. Here helps a restart and the path is set correctly afterwards
Reference(setbuf): https://bugreports.qt.io/browse/QTCREATORBUG-3994