You are correct - the reference line option is not available in the combo chart, I am not sure if it will be added, but I will inform our PM group.
In the mean-time - you can possibly calculate a trend or reference line using Qlik expressions. Check out the sample and solution to this post: http://community.qlik.com/message/590193
Let us know how you do.
Please mark the appropriate replies as correct or helpful so our team and other members know that your question(s) has been answered to your satisfaction.
Hello Michael- Do you know if the Reference Line functionality made it into the pipeline for the next release? This is a very useful feature. I have a set of incident data that I am working to visualize on a combo chart. It will have the date of the incident and the length of time it took to resolve. Is there a way to add a solid horizontal line to the chart showing the Mean Time to Resolution (i.e. Average incident length) over all the date dimensions. Your equation referenced above almost gets there but I don't want trending.
Thanks for the help!