Please have in mind that sometimes after you leave integrated menu by default in appearance->menus, and then after changing something go back to menus you may find that MDF megamenu fields are not visible. Please do not panic all fields are saved and in place, it's just that they are not visible at the moment because current menu ID is not passed by url in wordpress admin - go here for details if that happens to you.
The above mentioned issue is resolved in latest release, make sure that you are using latest version. Thank you for using MDF Megamenu
MDF Megamenu - Tutorial 01
MDF Megamenu - Tutorial 02
MDF Megamenu - Tutorial 03
MDF Megamenu - Edit Megamenu Size
MDF Megamenu - Add Icons
MDF Megamenu - Add Widgets
MDF Megamenu - Add Tabs
MDF Megamenu - Top Menu
MDF Megamenu - Side Menu
MDF Megamenu - Display Menu Only On Selected Pages
If custom elements (megamenus, columns, and similar custom data) are not displayed in menu elements after you come back to appearance->menu and your default menu (on which MDF is integrated) is not showing custom details like green colored text "megamenu" dropdown sizes, and column content it means that menu ID is not sent through url like it should when menu selection is confirmed. So to fix this, just re-select the current menu by clicking select for Select a menu to edit: option in the top left corner.