You can try Structure plugin, which can aggregate estimates upwards in the hierarchy - but you'll need to create a "meta-issue" representing the total, and then add all issues from the backlog under that "total" issue as sub-issues (you can use the same JQL condition as advised by Mathias).
In this way you can also have totals per-epic.
Disclosure: I'm working for the company behind Structure
Hey admins! I’m Dave, Principal Product Manager here at Atlassian working on our cloud platform and security products. Cloud security is a moving target. As you adopt more products, employees consta...
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