Filter Feature Flags by status
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### Problem to solve
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If we have a long list of feature flags, the users would need to filter it in order to focus on the filter that interests them.
### Intended users
<!-- Who will use this feature? If known, include any of the following: types of users (e.g. Developer), personas, or specific company roles (e.g. Release Manager). It's okay to write "Unknown" and fill this field in later.
* [Parker (Product Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#parker-product-manager)
* [Delaney (Development Team Lead)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#delaney-development-team-lead)
* [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer)
* [Presley (Product Designer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#presley-product-designer)
* [Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer)
* [Sidney (Systems Administrator)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sidney-systems-administrator)
* [Sam (Security Analyst)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sam-security-analyst)
* [Dana (Data Analyst)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#dana-data-analyst)
Personas are described at https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/ -->
* Developers who create feature flags
* QA engineers enabling/disabling flags
* Release managers who want to control which features are released and to which customer base
* Support engineers that wish to release features to beta customers or test version to fix bugs for specific customers
### Further details
<!-- Include use cases, benefits, and/or goals (contributes to our vision?) -->
A user case can be you want to look at one environment and see what feature flags are set for it.
### Proposal
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Create the ability to filter by:
* Feature flag status
* Enabled
* Disabled
| Description | Mockup|
| ------ | ------ |
| Filter dropdown |  |
| Select option |  |
### Permissions and Security
<!-- What permissions are required to perform the described actions? Are they consistent with the existing permissions as documented for users, groups, and projects as appropriate? Is the proposed behavior consistent between the UI, API, and other access methods (e.g. email replies)?-->
### Documentation
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Add all known Documentation Requirements here, per https://docs.gitlab.com/ee/development/documentation/feature-change-workflow.html#documentation-requirements
If this feature requires changing permissions, this document https://docs.gitlab.com/ee/user/permissions.html must be updated accordingly. -->
### Testing
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### What does success look like, and how can we measure that?
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### What is the type of buyer?
<!-- Which leads to: in which enterprise tier should this feature go? See https://about.gitlab.com/handbook/product/pricing/#four-tiers -->
### Links / references
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