This is the documentation of JSU for Jira Server/Data Center. If you are using JSU on Jira Cloud, you can find the documentation here.
The 'User Is In Custom Field' check will verify that the current user is in the specified custom fields, (typically a multi select/user picker custom field) Note, this check only applies to custom fields.
You must specify the field that is the prerequisite for this transition, and whether the user must be in the custom field or not, when configuring the check. For example:
For information on how to configure a check for a workflow transition in JIRA, see the JIRA documentation.
A workflow is configured so that the 'Close' transition has the 'User Is In Custom Field' check where the user must be in the 'User Select' field. A user viewing an issue in that workflow will not see the 'Close' transition unless their username has been selected in the 'User Select' field.
Supported Field Types