How to create a line chart with a circle at the joining end. I am showing a monthly number of users trend?

This can be done with the help of a dual-axis chart.

Let's say you need to create the yearly profit Trend. now you will be using year and profit as the major and dimension. Now drag the profit again in yourself and select dual-axis.

In the next option, select the first chart as a line chart and second as a circle. This way, you can create a line chart with a circle.