How to make a fixed column while navigating a webi report with many columns?

Hi experts,

I'm new to develop a webi report, and I accidentally view a webi report with the first column fixed while dragging to the right columns, so that users can still see he first column which has meaningful business infomation such as "ID", as shown in the attached picture.

I noticed it's only working in the "reading mode", not "design mode", could anybody show me how to do this?

thanks,
Jennifer