Hi,

You cannot change html structure of md-megamenu. You just choose one menu type that you prefer (standard/.../.../outright) and modify its style by create its own skin in folder theme. Then our Md Megamenu will generate option in setting allowing you to choose skin and color 

For example: 
+ Create a folder named megamenu_skin in your active theme folder
+ In folder megamenu_skin, you create 2 folders: skin_1 and skin_2, then create file megamenu_skin.yml ( the name megamenu_skin.yml is compulsory)
+ Write file css for skin 1, skin 2, using some available class of our megameu such as awemenu-default, awemenu-item,... or in buider tab css, declare class for elements and use these classes to write css
+ you can declare serveral skins in file megamenu_skin.yml. Each skin contains name, skin (file style for megamenu), color (color for mega menu - don not decalre if you do not need)

skin_1:
  name: Gold Skin 1
  skin:
    - skin_1/skin_1.css
    - skin_1/skin_1_fix.css
  color:
    - skin_1/color-a.css
    - skin_1/color-b.css
skin_2:
  name: Silver Skin 2
  skin:
    - skin_2/skin_2.css
    - skin_2/skin_2_fix.css

After finish, open with builder and you can see 2 newly-added skins (Gold Skin 1 and Silver Skin 2) apart from 2 skins: Default and Classsic
Note: You can name folder and file css the way you like but you must name file *.yml tobe megamenu_skin.yml

Also, please check your email

We have sent you update of required module to fix custom skin issue

You put folder megamenu_skin in a wrong location. 

You should place in your active theme folder. For example, core/ themes/bartik (not in megamenu module)

https://1drv.ms/u/s!ArRPkgVQNPYZgl2WeK6gxEuaNAP2