Could anyone give me an idea how to combine two credit card accounts, which are corporation credit card account with multiple credit card numbers, into one GL account?

Hey there, @sguan-novindevel.

You can merge your two accounts in QuickBooks Online (QBO) if you want to combine them. This way, it would be easy for you to track your transactions in your credit card account.

Let me show you how:

1. Go to Settings and select the Chart of Accounts.
2. For the account that you want to keep, click the drop-down arrow in the Action column.
3. Select Edit and take note of the name and detail type. Check if the Is sub-account option is marked. If it's marked, remember the parent account associated.
4. Click Cancel to return to the Chart of Accounts.
5. Look for the account that you don't want to use, click the drop-down list in the Action column, and select Edit.
6. Change the Name and Detail Type, then mark Is sub-account as appropriate.
7. Once done, select Save, then Yes to confirm.

In addition, here is the list of a few reminders when the merging accounts with sub-account option:

• If you’re merging parent accounts, make sure they don’t have existing sub-accounts.
• If you’re merging sub-accounts, make sure they are associated with the same parent account.
• If only one is a sub-account, make it a parent account by clearing the Is sub-account option.

Please take note that if you’re merging bank accounts that have reconciliation reports, make sure to save those reports first. 

Don't hesitate to tag my name in the comment section below if you have other concerns or questions. I'm always ready to help.