Im trying to set a condition in an Item Workflow for Non-inventory items and trying to set a field only if the Subtype is "For Resale" However, that option isnt available in the Conditions of the workflow action. IS there a way to use the Formula conditions to get non-inventory items for resale?

You could use a saved search condition instead - or create a custom field on the item record

The saved search doesnt work on create since the item wouldnt be in the search yet... i just find it very odd that netsuite doesnt allow the subtype field to be exposed in workflows

saved search would allow the item to be created, it does look like the subtype is available as a URL parameter before creation. You could possibly use a workflow action script to pull this and trigger whatever you need to happen