You can set post-functions based on CRM custom fields in workflow configurations:

Post-Function nameDescription
CRM function to clone issue based on Conditions set in workflow's transition
CRM Copy Contacts to Users PostfunctionFunction to copy contacts from the issue company field to a users picker field
CRM copy field value functionCRM function to copy value from a CRM field to Jira field
2019-04-19_14-40-27_Copy custom field value to CRMPost-function that fetchs the value from a Jira issue custom field to a CRM directory (Companies/Contacts) field