Help with Nav sub menu

[NewMedia]

I have nav menu set up in that one of the links has a submenu of the category pages within the link. For example, the link "Shop" in nav menu has this sub menu: category 1, category 2, category 3, etc.

There are several things I wanted to do with the sub menu.

1. When one is on Shop link, I want the submenu to automatically open and remain open when one is on the category pages under Shop. Therefore, I need to change the link from hover effect to toggle effect.

2. I'm trying to make the submenu horizontal. In order to do that, I need to change the display: block to display: flex. However, I was unable to do so. I tried adding a css class cuz I noticed that .highlighted appears as one hover over the link with submenu. However, it didn't work because the submenu has inline styles added.

.mb-primary-nav-menu .highlighted ul.sub-menu {    display: flex !important;    justify-content: center; }

Also, you can see how the code functions in the screenshots below, with hover and without hovering over the "Shop" link.