I just changed the version of Cadence Allegro from 16.6 to 17.2.
In the Part Developper (Symbol view) in 17.2 the display with the symbol created is missing, see below the picture:
In 16.6 there was this display to modify the symbol on this window.
Now we have to right click on "sym_1" and select "Edit (in DE-HDL)" to modify the symbol.
Do you know how I can have the display in this window in 17.2 ?