The 'LOGICAL ZOOM MODE' allows you to display subtrees within the tree display area of the 'ARB_NT' window.
Click on the <LZoom> button of the 'ARB_NT' window or press the 'F5' key on the keyboard to activate the 'LOGICAL ZOOM MODE'. In the latter case, the cursor has to be placed within the tree display area.
Display a subtree:
Move the cursor to that internal node of the displayed tree (section) which defines the subtree and click on the left mouse button. The subtree-defining node is that located closest to the indicated root (open square) of the whole tree which directly or indirectly connects all branches of the subtree.