draftOrderUpdate lineItems

I am looking to add a Line Item to Draft Orders via Shopify Flow and an Admin API request. I currently have the following issues:

  1. It appears that I need to include the existing Line Items in the input and I am not sure how to do so.
  2. I am attempting to use priceOverride to track this Line Item as a product with custom pricing, and it does not seem to be available in this version.

Any guidance would be much appreciated. Thank you!

Managed to handle the previous line items with a for loop. Still looking for the best way within Admin requests in Flow to set a custom price. Thank you!