How to resize a mask selection in Premiere without losing its shape | Worst usability ever?!
Watch me struggle resizing a square mask in Premiere Pro CC 2017
To resize maintaining proportions:
1.- Place cursor outside a corner (cursor will change to arrows)
2.- Press Shift key and left-click mouse drag outwards/inwards
To move a side/wall of the square
1.- Shift + left click a corner
2.- Shift + left click the other corner
3.- Release shift
4.- Left click drag one of the corners in the direction you intend to move it towards
Have fun!