The rotated working plane can now be used for drawing an object, such as a staircase, for instance.

After setting an appropriate placing grid - use the " Grid snap properties" .

Base Object > Prism

Start with the design of a staircase using the command " Place new prism".

Draw object in the 3D view.

Each mouse click on your working plane creates a new point. 

After you have defined the last point, terminate with " Return" or double click the last point. 

To exit the edit mode, press " ESC" .

Note:  during the "Draw cube with the mouse" command, you can undo wrong entries with " Backspace".

Enter your input with " Return" or double-click the last point.