I'm here to help track your markups in QuickBooks Online (QBO), ld-kore.

QBO will automatically set a default account once your turn on markups. If you need to use other income account, you can create a new one. 

Let me show you how:

1. Go to Settings ⚙ and select Chart of Accounts.
2. Click New to create a new account.
3. From the Account Type ▼ drop-down, choose an account type.
4. From the Detail Type ▼ drop-down, select the detail type that best fits the transactions you want to track. 
5. Enter a name, like Markup.
6. You can add a description.
7. When you're done, select Save and Close.

You can then assign the newly added account. Here's how:

1. Go to Settings ⚙, then Accounts and Settings.
2. Proceed to the Advanced tab.
3. Click Chart of Accounts, then select the account from the Markup income account drop-down list.
   
4. Click Save, then Done.

Once all set, you can start entering billable expenses to incur customers with markups.

Upon sharing this solution, I still suggest consulting your accountant. They can provide specific instructions if you need to use a different account to track markups.

Don't forget to click the Reply button below if there's anything else you need about this. Just tag my name, and I'll get back to you.