Assigning bank opening balance to owner's capital contribution.

Hello there, ddisimone.

The option to take and assign an opening balance from one bank account to multiple accounts isn't available in QuickBooks.

As of now, we'll have to assign an opening balance manually. 

You can refer to this article for more information: Enter Opening Balances For Accounts in QuickBooks Online.

I'm just a post-away if there's anything that I can help. Keep safe!