There is a dedicated topic for WinBox 4 in Announcements and this issue is known. Currently you need to use ‘Download…’ button on the right panel of Files window. And no, UI has degraded compared to v3.
Thank you for the response. Finally, I am now able to copy at least the .backup and .rsc files from the MT to my PC. Unfortunately, I can’t download the folders and other files like the Hotspot Folders and some netwatch messages.