Offline installer cannot browser and install QBSP file without Internet connection

The steps described here;
https://doc.qt.io/Boot2Qt/b2qt-qbsp-installation-guide.html
cannot be done without Internet connection. The 'browse QBSP file' button does not exist if not connecting to Internet.

What I expect is that the pre-downloaded QBSP file can be installed by offline installer without Internet connection.