Polygon Tool
Activate the tool, then select consecutively at least three existing points (or click at least three distinct positions in the Graphics View) which will be the vertices of the polygon. Click the first vertex again to "close" the polygon.
Holding down the Alt (MacOS : option) key after selecting a vertex of the polygon allows to create the next vertex such that the side between these two points makes with the preceding side an angle that is a multiple of 15°.
