Add or delete a group in a paginated report chart (Report Builder)
Applies to: 
Microsoft Report Builder (SSRS)
Power BI Report Builder
Report Designer in SQL Server Data Tools
In paginated reports, select the chart data region to display the Chart Data pane. Create groups by dragging dataset fields to the Category Groups and Series Groups areas. To add nested groups, add multiple fields to the area.
Note
You can create and modify paginated report definition (.rdl) files in Microsoft Report Builder, Power BI Report Builder, and in Report Designer in SQL Server Data Tools.
Add a parent or child group to a chart
On the report design surface, select the chart. The Chart Data pane appears.
Drag a field from the Report Data window to the Category Groups or Series Groups area. To add a parent group, position the cursor in front of an existing group. To add a child group, position the cursor after an existing group.
Edit a category group on a chart
On the report design surface, select the chart. The Chart Data pane appears.
Right-click the group in the Category Groups area, and then select Category Group Properties.
Add or remove group expressions, filters, sort expressions, and group variables.
Select OK.
Edit a series group on a chart
On the report design surface, select the chart. The Chart Data pane appears.
Right-click the group in the Series Groups area, and then select Series Group Properties.
Add or remove group expressions, filters, sort expressions, and group variables.
Select OK.
Delete a group from a chart
On the report design surface, select the chart. The Chart Data pane appears.
Right-click the group in the Category Groups or Series Groups area, and then select Delete.