isCOBOL Evolve : User Interface : Controls Reference : TREE-VIEW : Styles : Flat
Flat
When this style is set under the Windows Look & Feel, Tree-View buttons are replaced by chevrons and connection lines between items are not shown.
 
Example - Define a tree-view with a “Windows 10” style:
...
screen section.
...
  03 screen-1-tv-1 Tree-View
     flat
     line 2.7
     column 3.4
     size 20.8 cells 
     lines 29.1 cells 
     height-in-cells
     color 144
     id 2
     .