In order to apply workflow-based permissions, please follow the next steps:
Log in as a user with the 'Jira Administrators' global permission.
Navigate to Admin menu → Issues. Select Custom fields permission schemes.
Click the Add Scheme link, enter the name and optional description → Save.
In the Operations section click Permissions, apply desired permissions you want to add at particular status for your secure field(s).
Navigate to Admin menu → Issues. Select Workflows and locate the workflow of a needed project → Edit.
Select status for which you want to apply secure fields permissions and click on Properties → Add New Property.
Property Key: com.coresoftlabs.secure-fields.field.XXXXX.scheme, where XXXXX - id of secure field.
Property Value: id of newly created permission scheme.
7. Click Add and publish the workflow.