Q: How do I make the submenus stay at top? I am developing a Magento2 webshop, I have bought a theme to use, but I want to change the look of the megamenu so that the submenu fills the same height as the original menu and so that the submenu starts at the top of the menu and not at the top of the list.



A: Maybe you could share some of the code (in a codepen or something similar) so I can see the structure. But here's a snippet of what I think you want to achieve.
https://codepen.io/europarising/pen/xNJqVj
 .categories {
   display: flex;
   flex-direction: row;
   flex-wrap: wrap;
   align-self: flex-start;
   border: 2px solid red;
   padding: 10px;
   width: 1000px;
   height: 300px;
   overflow: hidden;
   overflow-y: auto;
 }

 .categories__layer1 {
   list-style: none;
   padding: 0;
   margin: 0 0 20px 0;
 }

 .categories .categories__layer1 > li {
   display: flex;
   flex-direction: column;
   flex-wrap: nowrap;
   align-self: flex-start;
   padding-right: 20px;
 }

 .categories .categories__layer1 > li span {
   font-weight: bold;
 }

 .categories__layer2 {
   display: flex;
   flex-direction: column;
   flex-wrap: wrap;
   align-self: flex-start;
   list-style: none;
   padding: 0;
   margin: 0 0 20px 0;
 }

