Thank you for posting in the Community. Allow me to help share some insight about recording a split bill payment in QuickBooks Online.
You can list your company as a vendor twice to create bills for each. This way, you can enter 2 split bill payments with the same amount for a different vendor. Just make the second name slightly different, like adding a period so that QuickBooks will take it.
Let me show you how:
From the left menu, select Expenses.
In the top right corner, select New vendor.
Enter all necessary information.
After that, you can now make a vendor payment form the Pay Bills page.
Select the Plus icon (+) on the Toolbar.
Under Vendors select Pay Bills.
Select the appropriate Payment account and enter or verify the Payment date.
Click the Filter icon to narrow the list of bills to view only those you specify, and select Apply.
Select the checkbox of the bill to pay.
Enter the amount of the Payment to be applied to the open bill.
Select Print then select Save and close or Save and new.
I've attached an article about changing the display name and bills for additional reference: