As for the reposition element action, the resizing action can also be made from the canvas, for your own convenience. But as for repositioning, adjustments made from the canvas are not accurate and sometimes could not be enough.
On the Properties panel of the element, you will find the numeric values of width and height. Click on the element in the timeline or the canvas to have access to their properties and change its size. On the General submenu, provide the variables of the new size; you may block and unblock the aspect ratio and reset variables to the original settings.