The Crosshair mode can be activated form the Target button in
the main APT screen or with Alt+T shortcut.
Combined with LiveView or taken image the Crosshair mode can help in alignment tasks like: Drift Alignment, GoTo Alignment, Precise mode checks for Meade mounts and everything that needs a benchmark. 
Here are some key combination that gives more control over the Crosshair:
Centered cross:
Moved cross:
Rotated cross: