Dark Mode Styling Widget Tutorial
Essential Classy Tab from Dashboad -> Widgets then enable Dark Mode Styling Widget
Now Drag and Drop Dark Mode Styling widget
Text form Normal & Dark Mode, You can use smiley emoji
Body Background
Global Color same as Elementor Global Color Sequence
Style Tab
Button
Manage padding of button.
For normal and Active/Dark mode you can manage Color, Background, Border and Box Shadow.