Thank you for the screenshot.
The desired functionality is not provided out-of-the-box. On this thread you will find information about two possible approaches using plotbands or using a new line series. You will also find example demonstrating each of them.
A third option would be to use the rangeColumn Chart. You will see that the data configuration is an array of arrays. You can pass values with very small difference (e.g [5, 5.1]) so that the rangeColumn would look like a line. However, this solution would require you to calculate the offsets manually by first getting the values for the data configuration from the DataSource. If you settle for this approach, I would recommend a careful testing to avoid any undesired results.
I hope I was helpful. Let me know if you have any further questions.
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