A Style can be copied and then pasted by selecting a style in the upper left pane and then use the Copy icon.

Alternatively, use the File pull down as shown below.

Or right mouse button selecting Copy.

This can then be pasted by using the Paste icon.

Note the name of the copied style is now shown in the right hand box at the bottom of the window.

Alternatively, use the File pull down as shown below.

Or the right mouse button in the upper left pane.

This will bring up a dialogue box for you to enter the name for the new style.

Note that a default name is there already based on the style being copied.

Enter the name and click OK.

The style can then be modified as required.