Files always open in main window

Hello, this is regression comparing to Qt Creator 4.xx.xx.

Old behavior (OK) (Qt Creator 4.xx.xx): in multi-window mode, files always opened in active window; Here is the video, how did it work with Qt Creator 4.14.0: OK.mkv (or youtube link https://youtu.be/E56Zv5TtwEw)

Current behavior (NOK): in multi-window mode, files always opened in main window;
Here is the video, how does it work with Qt Creator 6.0.1: NOK.mkv (or youtube link https://youtu.be/WcuG8Tm3IdY)