That "stripped down" dialogue window is Qt non-native file dialog window instead of the native Windows file dialog. This was done to prevent a crash caused by the Windows native dialog box allowing the user to hand enter an external urls when it was explicitly asked for file paths.
See this thread for the bug report about the crash and the resolution:
https://www.mobileread.com/forums/sh...d.php?t=368479
FWIW, it is not actually "stripped down". It is just different. You can hand type any path and drag its folder into the left hand side window pane and it will be remembered and be there for future use. Everything you need to do with the native dialog can be done with the Qt non-native dialog. Plus the non-native dialog is safer and prevents crashes on Windows.