It's nice to see you here in the Community forum, nav-dugmore.
In QuickBooks Self-Employed (QBSE) , you can manually add transactions to track your expenses.
Here's what you'll need to do:
For your visual reference about this process, you can check below screenshot:
As for your concern, if you can put them as travel expenses without having a receipt, I recommend checking with your accountant. They can guide you on what is the best thing to do in this situation.
If there's anything else you need help with in managing your transactions, let me know by commenting below. I'm here for you. Have a great day!