Change submenu markup

The whole idea of a custom walker class is that you can customize the menu in detail. So, you can also leave the main menu as it is and build the submenus the way you give in the image. However, as Hareesh indicates in the comments, this does require quite a lot of customization, especially … Read more

Update configured themes

As per comments, courtesy Matthew, this seems to be the best option: I think your brainstorm is the best option. You should get them all child themes and then going forward it will be way less of a hassle to update. It shouldn’t take too long. Just figure out which files were customized, through them … Read more