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See this section of the documentation for more information on assigning the workload scheme.
Modifying the Default Scheme
The default workload scheme ensures that all new Jira users are automatically assigned a predefined workload distribution, simplifying the onboarding process and maintaining consistency.
To replace the existing default scheme, click the 
icon next to the desired new workload scheme. After this change, all new users added to the Jira instance will be assigned this schema by default.
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Managing and Editing Schemes
Once a workload scheme is created, there is no way to edit it. But you can archive and delete unused or erroneously created schemas.