The feature allows to filter issues on boards by users and by summaryAgile Filters for Jira add-on provides useful filters for JIRA Software Boards.
Without the sorting by users feature you had to create as many quick filters as assignees you have in your company.
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Then go to the board and select user in the assignee field to filter issues (the dropdown list shows first 20 matches):
Also the feature allows to search by summary field. When you enter the board all issues are opened that correspond to quick filters enabled.
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