The panel as it will appear in the header, on a page, so it can be measured before it goes anywhere near the header. Destinations are the ones in Megamenu links.rtf.

Mega menu

What you can do

The panel exactly as drawn. The header is the one element that changes on all 194 pages at once, so it is measured here first.

The two highlights are not in this markup

«You are here» and the highlight under the cursor are CSS, generated beside the panel and shipped as WPCodeBox snippets. They are visible on the header, not here.