Once you test out the configurations in Sandbox, go to your Sandbox account, navigate to Admin -> Sandbox in Service Desk Productivity
Click on View Changes to fetch all the changes made in your Sandbox account.
You can then click on Regenerate Change List -> Regenerate to ensure all the changes created are included in the change list before syncing them.
If there aren’t any conflict or sync errors shown in the change list, you can go ahead and click on Sync Now to have these changes synced to your Freshservice Account.
Once the sync is successful, your sandbox account will automatically get destroyed.
