Add, change, or remove error bars in a chart - Microsoft Support
You can set your own values to display the exact error amounts you want. For example, you can show a 10 percent positive and negative error amount in the results of a scientific experiment like this: You can use error bars in 2-D area, bar, column, line, xy (scatter), and bubble charts.

Add or remove series lines, drop lines, high-low lines, or up-down bars ...
Excel for Microsoft 365 Outlook for Microsoft 365 More... You can add predefined lines or bars to charts in several apps for Office. By adding lines, including series lines, drop lines, high-low lines, and up-down bars, to specific chart can help you analyze the data that is displayed.

Add a trend or moving average line to a chart - Microsoft Support
Learn how to add a trendline in Excel, PowerPoint, and Outlook to display visual data trends. Format a trend or moving average line to a chart.

Modify chart legend entries - Microsoft Support
When a chart has a legend displayed, you can modify the individual legend entries by editing the corresponding data on the worksheet. For additional editing options, or to modify legend entries without affecting the worksheet data, you can make changes to the legend entries in the Select Data Source dialog box.

Add or remove data labels in a chart - Microsoft Support
Add data labels to a chart. Click the data series or chart. To label one data point, after clicking the series, click that data point. In the upper right corner, next to the chart, click Add Chart Element > Data Labels. To change the location, click the arrow, and choose an option.

Add and format a chart legend - Microsoft Support
Format a chart legend. Customize a legend. Steps for adding and changing the look of a chart legend in Office 2016 for Windows, including customizing the border, the background of the chart legend, and changing and resizing the font used in a chart legend.

Edit titles or data labels in a chart - Microsoft Support
On a chart, click the chart or axis title that you want to link to a corresponding worksheet cell. On the worksheet, click in the formula bar, and then type an equal sign (=). Select the worksheet cell that contains the data or text that you want to display in your chart.

Vary the colors of same-series data markers in a chart
When you create a single-series chart, all data markers that represent the data points in that data series are displayed in the same color. To use different colors for each data marker, you can vary the colors automatically by using the Vary colors by point or Vary colors by slice option.

Add or remove a secondary axis in a chart in Excel - Microsoft Support
In the chart, select the data series that you want to plot on a secondary axis, and then click Chart Design tab on the ribbon. For example, in a line chart, click one of the lines in the chart, and all the data marker of that data series become selected.

Change the plotting order of categories, values, or data series
Reverse the plotting order of categories or values in a chart. On a chart, do one of the following: To change the plotting order of categories, click the horizontal (category) axis. To change the plotting order of values, click the vertical (value) axis.