I'm here to share a few information about splitting paychecks into separate General Ledger (GL) accounts, Thomas.
For now, this option is unavailable in QuickBooks Online (QBO). You can continue utilizing the class feature to differentiate portions of your paycheck. Once done, you can run the Statement of Activity by Class report to see those payroll transactions assigned to classes. You'll only have to make sure to click the amount to drill down the transactions:

You may want to update your payroll accounting preference, here's an article for detailed guidance: Change your Accounting Preferences in QuickBooks Online Payroll.
Additionally, if you need extra guidance while making changes to your payroll information in QBO, I have these articles for you:
Post a comment below if you have any other concerns when splitting paychecks and assigning to a different GL accounts. I'm always right here happy to assist you further.