Yes, you can split transactions to record them in multiple accounts in QuickBooks Online, @David. I'd be happy to walk you through the process.
If you already have recorded a check and want to split it into different categories, you can do so by following these steps:
- On the left pane, go to the Accounting menu and select Chart of Accounts.
- Click the View register link for the account where the check was posted.
- Press the check then click the Edit button to open its window.
- Add the other accounts in the Category details section.

- Tap Save and close.
After that, you can check your Chart of Accounts to see if it shows up as split transactions. Here's a sample screenshot for a visual reference:

See this article to learn more about recording multiple accounts in a transaction: Enter a split transaction into the register.
I've added these resources that tackle how COA and checks work to the program:
I'm just one post away if you need a hand with splitting checks or managing your accounts. I'd be pleased to help you out. Take care always.