Something every SketchUp user should know, as it’s a huge modeling time-saver, is how to create multiple copies of an object with the move tool. This is sometimes called a “linear array” on other software.
We think it’s a cool way of creating a stair:
Draw a rectangle and make it into a volume using Push/Pull; Select your newly created stair thread element and press G to make it into a component.
Pick the Move Tool, press and release Ctrl on your keyboard and use the mouse to create a copy as shown.
Just after clicking to finish the first copy, type the number of copies you want followed by X or * and press Enter.
Done, a basic stair using multiple copies.