Hi, I'm Tom Blessing. I'm an expert at helping small to mid-sized companies adopt Power BI. I'm also a recovering investment banker, with deep experience applying technology to otherwise manual data problems. I have dual degrees in Finance and Technology Management from Indiana University.

Resources to help build your fundamentals: Learning Power BI? Data fundamentals are critical for this process to be easier. I've assembled a few DataCamp courses to help. I earn a small commission if you click and purchase.

Introduction to Power BI course: Master Power BI basics and learn to build impactful reports.

Exploratory Data Analysis in Power BI course: Learn about Power BI's Exploratory Data Analysis (EDA) and enhance your reports.

Introduction to SQL course: Learn how to create and query relational databases using SQL in just two hours.

Introduction to DAX course: Learn the fundamentals of Data Analysis Expressions (DAX) such as calculated columns, tables, and measures.

Database Design course: Learn to design databases in SQL to process, store, and organize data in a more efficient way.

Stacked area charts are effective for displaying data as filled areas to show the composition of categories over time or other dimensions.

In some cases, you may want to add a line to a stacked area chart to represent a specific data series or to highlight a trend.

There isn't a built-in way to do this in Power BI. Meaning: this visualization isn't one of the options. 

But - In this guide, I'll walk you through a work-around to achieve what you want.

Creating Your Combo Chart

We're actually going to use a Line and Clustered Column Chart to achieve our combo chart.

• First Add a Line and Clustered Column chart to your canvas. 
• Add 2 data series that you want to graph to the Line Y-Axis wells. 
• Create a new single-value measure that is far outside the range of the max value of your dataset. For example, if the values you're charting range from 0 to 25, create a measure that looks like this: ChartArea = 500. Add it to your visualization as a 3rd line.
• Click back on your visualization and go to Format Your Visual > Secondary Y-Axis (this is the one that contains the lines). Manually set the Maximum to a value that's near the max value of your actual data set. In the above example, set it to 30. 
• Next, expand Lines and then expand Shapes and Colors. 
• Change the color of Chart Area (the manually added Measure) to a light grey.
• For the field where you want to show a Line, change the color to white. 
• Last, toggle on the 'Shade Area' switch. 

Boom! Now you have a stacked area chart with a line. You're options to change colors with this workaround aren't great, but you can achieve the combo chart type you want when it doesn't exist in Power BI natively.

Conclusion

Adding a line to a stacked area chart in Power BI allows you to highlight specific data series or trends within the context of your stacked area chart.

This combination of chart types can provide valuable insights and improve data visualization for your reports and dashboards.

Experiment with different configurations and formatting options to create compelling and informative visualizations that meet your specific data analysis needs.