You can't make the field increase in size, but you can make it "shrink to fit" for preview/print/PDF, but not browse views of your layout.
Resize the field to be very large, then use the Sliding & Visibility section of the Inspector's Position tab to set the field to "slide up". Since this change in field size may produce an undesirable blank space on your layout, you most often also want to specify "resize enclosing part".
Since such a large size field may be cumbersome for browsing and data entry purposes, it's often necessary to create two layouts, one with the field sized smaller, but equipped with a scroll bar for browsing/editing and one without the scroll bar, sized to be large, but also set to shrink/slide up.
Key facts about sliding:
- It's only visible in preview mode and when you print/save as PDF...
- All layout objects below and in the same layout part as the slide/resize field need to also be set to slide up and resize.
- Objects in headers and footers will not slide.
- Portals will shrink/slide to fit the number of rows of records, but fields within the portal row will not shrink/slide.
- Consistent side borders are difficult to achieve with sliding fields.