Yes, you can use your own existing metafield ( variant level ) with the Variant Description Block in the Neo app.
To do this:
Add the Variant Description Block to your product template via Online Store > Customize in your Shopify admin.
In the block settings, enter the Namespace and Key of your existing variant level metafield.
If the metafield exists for a variant, the block will automatically display the content
Note: The block will only appear if the metafield is present and contains a value for the selected variant.
This gives you full control to manage content using your existing metafields without needing to recreate them in the app.