CZML: create line glued to the label

I need to create a line that attaches a point on the ground to the “label” (that accommodates its “pixelOffset”).
I’ve been looking at the “label entity”, and it doesn’t seem to have anything like it.

I’ve used a billboard with a SVG created on the fly.

This is an old answer, but appears to still work in modern Cesium:

That post gave me the clue…