Designing superelement mesh: polygons limited to 4 points

When trying to build the superelement mesh, I draw polygons but as soon as I click on the 4th point, the system closes the polygon and I  have to start the next 4-point polygon. I know I can also use "import filter" and automatically draw my polygon from a dxf or shp file but in some cases it is useful to have the manual method available.
I use feflow 5.301 and the problem happens in the mesh editor and the new mesh editor.
When I load the superelement file from the tutorial the problem does not appear.

Thank you for your advices

The reason why FEFLOW closes the supermesh polygons with before setting the 4th point is that you have chosen quad meshing in the main menu. Only triangular meshing supports superelements with more than four sides.