Hi Joe, Team Omnisend here.
In case you want to pass additional data that isn’t passed by default, Alloy app could help with this. You can find more information here. It will help you build a couple of API workflows that will be passing data from Shopify to Omnisend and you can set up time or event based data syncs (e.g. order placed -> sync 'x fields to Omnisend').
What type of data you’re trying to pass? I could double check with the team if it's being passed by default or do you need an app for this.
Also, feel free to reach out to our Support Team at email@example.com or via Facebook messenger and they will be happy to help you out with this!
Hope that helps!