Hello,
Sorry, but it is not possible to stretch the main menu to the right of the header.
You can try increasing the font-size of the menu item to make the items take the space on the right side by using the following Custom CSS in the Custom CSS for Desktop area under Theme Settings >> Custom CSS.
.woodmart-navigation.main-nav .item-level-0 > a {
font-size: 21px;
}
Or you can try increasing the paddings of the menu items to make the menu go to the right side.
.woodmart-navigation.main-nav .item-level-0 > a {
padding-left: 20px;
padding-right: 20px;
}
Regards.
Xtemos Studios.