It is "Show compile dialog".
Yes the Wiki information is outdated. There was such a floating window a long time ago. It was removed when the compilation of packages became parallel with threads. Updating the progress information from many threads is challenging and the window was removed.
If somebody finds a way to restore it, great. A patch implementing it would be accepted for sure.
The Wiki page for env. Options has other errors, too. Settings have been renamed and moved around.