Please know that you can't change or modify the margins, but you can adjust your screen size to view all columns in your QuickBooks Online, Reba.
You can use the keyboard shortcuts to zoom in or out:
- Zoom in: Ctrl and +
- Zoom out: Ctrl and -
Alternatively, you can also use the horizontal scroll bar to move sideways and view additional columns in the expense table.

We're always here if you need further assistance running a report in QBO. I'll keep this thread open for your future reference.