For some reason the summaries of estimates are only shown in the backlog in Jira Cloud next-gen projects and not in epics. In epics you can see a summary based on numbers of tasks but this is less accurate since tasks takes different amount of time to complete.
This extension adds the same summary for epic details so you can get a much more accurate overview of how the work is going.
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Source: https://github.com/hengun348/Jira-estimate-summarizer
Extore is a team of professionals who are passionate about creating extensions for web browsers. This devotion also gives us opportunity to appreciate work of other people. We get inspired by useful, open source extensions made by developers all over the world. Our strong belief is that one should share helpful add-ons with others. That’s why we’d like to present you our ever-growing list of favourite extensions that have inspired us. Moreover, as you probably have already learned, sometimes struggling for the best brings an end to the good. Talking about add-ons it often turns out that an upgrade is worse then previous version. Also it can become really tricky to get back to the beloved version of your favourite extension. That’s why we’re going to make not only the latest, but all versions of our favourite (and we hope yours too) add-ons available for download. No more compromises, just stick to the version you really like!