Hi there, 

I appreciate you reaching out to the Communty about this. I'll be happy to answer your question and steer you in the right direction.

At this time, QuickBooks Online doesn't offer the ability to customize the space between rows and colums and increase the font size. I know how important this feature is to you and I encourage you to send feedback about this to our engineers. You can do this by clicking the Gear icon and looking for Feedback. New product ideas and improvements are largely based on the feedback we get from users like you. 

In the meantime, I encourage you to check out this helpful article from our Community. The article will show you how far you can customize your reports in QuickBooks Online. Here's the link: Customize Reports. Let me know if you have questions. I'm here assist.