Brilliant - that worked - (thanks for this tip - I didn't know about this).
One thing I did notice is that this works for one dropdown - but not the other that's been allocated the same style.
You can see the 'About' menu item is white, however the 'products' menu item is still transparent even though both have been allocated
background-color: var(--sppb-card-bg-variant-3);
Any ideas as to why one would work but the other doesn't?
Edit - I read your instructions properly and did it your way and unfortunately it doesn't seem to want to work.
I've allocated
.sp-megamenu-parent .sp-dropdown .sp-dropdown-inner, body.ltr .sp-megamenu-parent .sp-dropdown.sp-dropdown-main.sp-menu-right {
background-color: var(--sppb-card-bg-variant-menu);
}
to my custom CSS and can see it's allocated to the inner dropdown - but the variable isn't being picked up via the template manager.