Workflow Condition
Summary
Keychain introduces a new condition function to your system named User is a Delegate of.
This condition function allows only certain users to execute a transition, according to its configured delegation source and delegations defined on the Delegation Configuration page.
Just like other Jira condition functions, this condition function can be used in conjunction with other condition functions available on your Jira.

Condition Configuration
The condition function's configuration screen is shown below:

Delegation Sources (Allow Delegates of)
The function can be configured to get its Delegator from a number of sources.
The Current Issue referenced below is the issue that this condition is running on.
Assignee
If configured for Assignee, the field will take the assignee of the current issue as Delegator and will only allow the Delegates defined for that user to execute the transition.
Reporter
If configured for Reporter, the field will take the reporter of the current issue as Delegator and will only allow the Delegates defined for that user to execute the transition.
Project Lead
If configured for Project Lead, the field will take the project lead of the project (that the current issue is in) as Delegator and will only allow the Delegates defined for that user to execute the transition.
Single User
If configured for a Single User, the field will ask you to pick a user. Then it will use that user as Delegator and will only allow the Delegates defined for that user to execute the transition.
Project Role
If configured for a Project Role, the field will ask you to pick a project role. Then it will collect the users and user groups in the selected role (for the project that the current issue is in), use them as Delegators and will only allow the Delegates defined for those users to execute the transition.
User Group
If configured for a User Group, the field will ask you to pick a user group. Then it will use the selected user groups as Delegators and will only allow the Delegates defined for those users to execute the transition.
User Custom Field
If configured for a User Custom Field, the field will ask you to pick one of the Single User Picker or Multi-User Picker custom fields on your system. Then it will take the users in the selected user picker of the current issue as Delegators and will only allow the Delegates defined for those users to execute the transition.
Category
Category selection determines which delegation category the delegate will be based on.
If a specific category is selected, the delegator's delegates in the selected category and (since the General category implicitly includes all other categories) the General category will be allowed by the condition.
If the General category is selected, only the delegator's delegates in the General category will be allowed by the condition.
Dynamic Categories
It is possible to make the category selection dynamic, based on a field value on the issue.
When you choose “<Get category from issue field>” option as the Category, supported system/custom fields will be listed in a dropdown next to the category selection, and the user will be asked to select an issue field.

Keychain will look at the value of the selected issue field for each issue and try to match it with a category name. If it finds a match, it will use that as the category.
If the selected field value is empty, or there is no matching category, the General category will be used.
If the selected field is a multi-select field, Keychain will try to match all values with categories and use the delegates for all matching categories.
General category is always included.
Field values not matching a category name will simply be ignored.
If no values match a category name, the delegate list will include only the delegates for the General category (if any).
Delegation Policy
The policy selection determines how the condition function processes Delegations and determines the users to allow in the workflow.
See the Delegation Policies page for a detailed explanation of each policy option.
(The "Include Source Users" selection, which was available in old versions of Keychain, is superseded by the delegation policy selection)