MacMost has a good video on YouTube where he shares 10 macOS Catalina features. They’re smaller features that don’t get the same attention or shoutout by Apple, but they’re good to know. The first one he mentions is a feature that I noticed but was annoyed about. When you hover or long-click the green fullscreen button in Safari, it now brings up a menu window to enter full screen or tile the window to the left or right. While it makes this capability more obvious it also adds an extra step, when just dragging the window by the green button was faster. In any case the video is pretty helpful and you can watch it here.