Hello, @mickey-mickeymcc.
At this time, we aren't able to create journal entries in QuickBooks Self-Employed (QBSE). However, you can manually enter your transactions from the Transactions page. This way, they'll be added to your estimated tax calculations.
For your reference, check out these articles:
Also, read this article for additional reference about categorizing transactions in QBSE.
Keep in touch if there's anything you need assistance with. I'll be right here to help. Have a good day!