How do I extend the border line?
 

I would like to extend the orange line to the full width so it reaches the green line, please.

How do I do this?

https://prnt.sc/wb3t1w

My suggestion:

Remove the orange line and then apply "border-bottom: 2px solid orange" property to the header.

Eg

.canvas-layout-container .canvas-widget:not(.widget-no-border) .widget-header {
border-bottom: 2px solid orange;
}

Thanks.

All sorted.

Edited: OK thats fine, welcome

Our posts crossed :)

I fixed it using your code. I forgot a character which threw the CSS code haha.