Purpose With Nogroupbox you can replace all groupboxes by a title line (shown in blue).
Example Nogroupbox 
Format Nogroupbox

All group boxes are replaced by a title line.

Remark: When you use "signature" Design in SAP GUI, shifted fields and own elements within groupboxes become invisible  in some rare cases. This can happen for nested group boxes or group boxes below a tabstrip. With Nogroupbox you can avoid the problem.
In addition, complex screens with many group boxes often appear simpler with

Components GuiXT