Do you use any external tools? If not, have you at least considered using such to help you with the integration? You might want to take a look at ZigiOps - it's a flexible, no-code integration tool that connects Jira & SNow in a few clicks. It can be customized to fit your particular use case. You can take a look at it and decide for yourself if it might be helpful to your projects, feel free to book a demo or ask any questions if you want to know more.
Regards, Diana (ZigiWave team)