How can I create new styles?

The way to achieve this, is creating a new slide design: View>Master>Slide master.
On each slide design, you can change the styles via the context menu or the window Styles and formatting.
It is also possible to change the format / position of text frames etc.

By applying another slide design to a slide, you will have the according styles.

In Impress, you cannot create new styles for text and outlines in the window Styles and formatting.