Initially these features were provided by JSU but now on Jira Cloud they are maintained by Atlassian. The following workflow conditions are available:
- User Is In Any Groups Condition
- User Is In Any Roles Condition
- User Is In Custom Field Condition
- Value Field Condition
For information on workflow conditions in Jira, see the Jira Documentation.
Our JSU on Jira Server/Data Center documentation about Workflow Conditions will also give you some hints, how to configure them on Jira Cloud.