Horizontal Marker On XY Chart with Category Render

I have a chart that shows a value for a given employee number:


This uses the 'category' render option. I would like a horizontal line added at the 95 value. Is there a way to do this? I tried adding data that had Y values of 95 and x values of the max and min employee numbers and rendering that as a line, but that didn't work.

It should have worked.
Post the chart JSON and the data JSON so we can reproduce it.
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