Enable Trendline or Limit line on Charts

I would like to include a trendline to a scatter plot in the charts feature. For example I have a chart that has unique data points plotted... would be great to see a trend line inserted on top of the data.

Similarly... I want to put a metric line on a chart. For example if I have a scatterplot of data points... I want to insert a go/no-go line or a limit line to easily visualize the data points that are out of tolerance for the metric.

I really want to use this Aha! charts and dashboards for reporting to business leadership but without ability to visualize data against targets it is not possible to retire the excel files.