Choosing a Window background in the Inspector leaves it transparent

Choosing a Window BackgroundColour by clicking in Studio's Inspector colour picker can leave the Window background invisible. Starting from a new Window, the picker keeps the colour fully transparent even though HasBackgroundColour becomes True. Typing or pasting an opaque hex colour works. Choosing the first background colour should make it visible without requiring a separate opacity adjustment, while explicitly chosen transparent and semi-transparent colours remain supported.