You are most welcome.
Kindly check the screenshot below.

I am at the service -> contact page and "service" has a different color than the rest of the menus. Do you want add a background color to it?
If yes, then please add the following css rule in Cutom CSS section
.sp-megamenu-parent > li:active {
background-color: #eee;
}
About linked button: If you don't want to add new position from layout builder - you can add a menu item in the main menu, use "URL" as menu type, add a custom css class (as shown in the screenshot below) to behave like a button. If you create this way the problem will be - in lower resolutions (mobile, tablet) when the menu is hidden and shown in offcanvus - the button will also be hidden in offcanvus.

