Moving the PCB with shift held locks the PCB to increments of 45deg. This locks the movement of the PCB to 1 axis rather than it moving on 2. The 0.9.9 version has this feature, like previous versions, but it seems to be broken.
It will lock to one axis for left/right and the diagonal axes but up and down will not work now.
Win10
Version 0.9.9