### Release notes We've replaced the "epic" [filter](https://docs.gitlab.com/user/project/issues/managing_issues/#filter-the-list-of-issues) on listing pages with a more flexible "parent" filter that lets you filter by any parent work item, not just epics. This means you can now easily find child tasks by filtering on their parent issue, giving you better visibility into your work hierarchy and making it easier to track related work items.  ## Summary Add Parent filter component to work items list UI as part of https://gitlab.com/gitlab-org/gitlab/-/issues/536876. Make sure this filter is behind a feature flag [work_items_list_parent_filter](https://gitlab.com/gitlab-org/gitlab/-/issues/560366) till all of the operators are working without performance issues. ## Backend Support See https://gitlab.com/gitlab-org/gitlab/-/work_items/548093 ## Implementation Details - Add Parent filter component to work items list UI (when backend is ready) - A feature flag should control the filter on the UI - Support filter operations: - Equals (specific parent) - Not Equals - Wildcard (any/none) - Update filter state management and GraphQL queries - Integrate with existing filter system ## Acceptance Criteria - [x] Add a feature flag to control Parent filter - [x] Parent filter is available in epics list and project issue list - [x] All filter operations work correctly (equals, not equals, any/none) - [x] Filter handles epics and issues properly - [x] Filter integrates with existing filters - [x] Filter state is persisted in URL - [x] Unit tests added - [x] E2E tests updated ## Related Issues - Parent: https://gitlab.com/gitlab-org/gitlab/-/issues/536876 - Backend: https://gitlab.com/gitlab-org/gitlab/-/issues/510269 - Blocking: Backend performance issues (18.2 milestone) - Iteration 2 for parent filter: https://gitlab.com/gitlab-org/gitlab/-/issues/560430 - Feature flag rollout issue: https://gitlab.com/gitlab-org/gitlab/-/issues/560366