I'm familiar with how to move a line up or down in other editors, like Atom and Sublime.
How is this done in Visual Studio Code for Mac?
In Visual Studio Code for Mac...
To move a line UP: ⌥+↑ (alt + up arrow key)
To move a line DOWN: ⌥+↓ (alt + down arrow key)
See here for a reference on Basic Editing Key Bindings in Visual Studio Code.