There is an Environment Overrides panel in the toolbar on top of Xcode's Debug Area. It allows you to select some of the most common accessibility options and Dynamic Type sizes, like in the Accessibility Inspector, plus select dark/light mode.

There is a panel with options called, Environment Overrides. It can be found in the toolbar on top of the Debug Area, the area with the variables view, and the console. It contains three sections: appearance, where you can select light or dark mode; dynamic type to change the text size, and accessibility, with some of the most common options (increase contrast, reduce transparency, bold text, reduce motion, on/off labels, button shapes, grayscale, smart invert, differentiate without color).