Yes, please reach out to Basil Support to have QuickBooks Online enabled on your account first. Once enabled, go to your Profile (https://basil.coraltreetech.com/settings) and go to Invoice Settings. Set the toggle to 'Enable' and follow the subsequent prompts. Once enabled, when you go to the People tab of Basil, you will see a QBO button at the top-right which you can use to merge and import your list of clients in QuickBooks Online. Clients who have been successfully merged will have a green 'qb' logo next to their name.
When creating an Invoice in Basil going forward, as long as the Client you're sending the invoice to has been merged or imported through QBO, you will have the option to 'Send to QBO' to have your Invoice sent to your QuickBooks Online account for you to then edit and send from there.