I've got you covered in enlarging your QuickBooks view. Let's get this sorted out.
If you wish to change the font size for better viewing of your QuickBooks Online, you can hold the "Ctrl" key and press the "+" sign simultaneously on your keyboard. Or, you can hold the "Ctrl" key and then use the mouse to scroll up.
Also, you can click the magnifying glass icon at the upper right corner and hit Reset to adjust the web browser display.