Currently, we're unable to enter a supplier's bank details in QuickBooks Online (QBO). Though, you can keep a copy of their bank details.
You can also find a third-party application that can help handle the information. You can visit our QuickBooks App Store and look for an app that integrates with QBO. Or, you can go to the Apps menu in your QBO account and look for an app from there.
While we continue to develop new features in QuickBooks that can help you save time, I recommend you regularly check our QuickBooks Blog for the latest feature available in QBO.
Also, I encourage checking our Help articles page to learn some tips and tricks in managing your QBO account. From there, you can read great articles that can guide you through the steps by steps process.
Don't hesitate to drop a comment below if you have other questions. I'm more than happy to help. Take care!