how can I change expense name / categories to match my business in QB Self Employed?

I can share some information about the expense categories that we have, @alexandra11.

We are following the HMRC's SA103F categories for self-employed individuals. The feature to customise or change the category names in QuickBooks Self-Employed (QBSE) is currently unavailable. 

Here are the SA103F expense categories you can claim as allowable expenses for self-employment in QBSE: About SA103F Categories.

I've also added this helpful article to give some insights on how QBSE tracks your business income and expenses: QuickBooks Self-Employed Overview.

Feel free to post here again if you need further assistance in categorising your transactions in QuickBooks. I'm always around to help. Have a good one.