A track piece on the grid can be selected by clicking it. Multiple tracks can be selected by clicking and dragging with Shift key down or by shift-clicking on two track pieces.
Dragging with Shift key down from (A) to (B)
Clicking (A) and (B) with Shift key down
Resizing a Layout
If you want to resize the layout then select the menu item "Layout Size..." in the Track menu. The layout is expanded or contracted in every direction from selected base location. The layout can be as large as 99 columns by 99 rows. However, if the layout is very large, the 3D view may become too slow if you don't have a very fast computer.
Layout Size window