By default you can't have the velocity chart of the scrum board which shows historical velocity to be available on the dashboard.
You can use plugins like this - https://marketplace.atlassian.com/apps/1215768/agile-velocity-chart-gadget?hosting=server&tab=overview
Or reporting plugins like eazyBi or Dataplane.
eazyBI indeed allows reporting on multiple sprints on the same report.
Here is an example of Multiple sprint story points burn down report: https://eazybi.com/accounts/1000/cubes/Issues/reports/201445-active-multiple-sprints-story-points-burn-down
In the given example, the report is designed to analyze data in all active sprints.
You can publish eazyBI reports and dashboards using Jira or Confluence dashboard gadgets: https://docs.eazybi.com/eazybijira/publish-reports/eazybi-gadgets-in-jira-dashboards
Ilze, eazyBI Customer Support Consultant
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