I have a expense that has already been reconciled. I wanted to know, is there a way to still split this expense, after it's already been reconciled??

If by splitting you mean split expense into different lines then yes, you can. 

Just make sure that the total amount after splitting is same as before to avoid discrepancy.

Yes, I need to split the PREVIOUSLY reconciled expense into two (2) different expense categories.  When I try to go back and make the split, I receive a notification, "that this expense has already been reconciled".  I realize the split expense needs to total up to the original expense amount. My true question is, how do I go back and split a expense between two categories, after the expense has PREVIOUSLY been reconciled? 

Let me help you how to split the reconciled expense between two categories in QuickBooks Online (QBO), Derrick.

When splitting a reconciled transaction, let's ensure that the total amount between the two is the same as the original amount to avoid discrepancies when making changes.

Here's how to open the expense transaction from the bank register:

1. Sign in to your QBO account.
2. Click on the Settings icon and select Chart of Accounts.
3. Choose the bank account associated with the expense, then click View Register.
4. Select the expense transaction you want to split, then click Edit.
5. To split this expense transaction, select another Category on the second row and enter an Expense for the Description.
6. Also, make sure to split the original amount of the expense transaction. For example, if the total expense amount is 500, then we can split the amount into 250.
7. Once done, Click Save and Close.

I've attached screenshots for your reference:

Furthermore, let's run a reconciliation report to confirm the accuracy and validity of financial data: View, print, or export a reconciliation report.

Feel free to comment below if you need anything else with splitting a reconciled expense. I'd be happy to assist.

Whenever you make ANY changes (description, chart of account, date, terms etc) to a reconciled expense transaction you will always get "that this expense has already been reconciled" notification. Thats normal.

The transaction you are editing has been reconciled. Saving your changes could put you out of balance the next time you try to reconcile. Are you sure you want to modify it?

You can click "Yes"

Thank you so very much for the detailed instructions/directions! I was able to make the modification.

Thanks again,