A pleasant day to you, @ceo9.
To help verify if the process of sending an invoice in Arabic to your customer through API's, I recommend contacting our Intuit Developer Team. This team is the best resource for such inquiries as they'll be able to discuss with you about the API operations on QuickBooks Online company data.
To reach our Intuit Developers, please visit this link: Intuit Developer.
I've also added here some links about customizing and emailing invoices in QBO for reference:
Know that I'm just a post away if you have any other questions. I'll be around to help. Take care, ceo9.