I see what you mean, It snaps to the middle horizal en vertical points in the middle of the screen...... That is indeed annoying.
I suggest that you (on behalf of all of us) submit a request for change using the Rate use & Provide suggestions, behind the File menu tab.
In the meanwhile, try this: In the shape designer, switch from properties to keyframe. In the object settings there is the ability to change the X and Y positions. When I do that (e.g. with up and down arrow the object moves and does not seem to snap to the middle lines. Before you do so, I think, you should size and shape the shape to your wishes and then do the fine positioning.