I am looking at how much time consultants spent on the phone and the traget is about 20%. How can I manually add a horizontal line that shows 20%?
I would consider using a bullet chart because it has a Target Value field that is helpful to use in a case like this. You can create a beast mode field called target and put in a value of .20 and then drag this into the target value field. You might need to choose the aggregation type of Average, depending on your data.
You could also do this with a line+bar chart and have your target value be the y-axis and the consultant values be the series.