The only way I know of to align objects (other than individual control points) in a Model window is to place your original object so a horizontal or vertical side are on a grid line, then turn on "Snap to Grid" (it's a button in the top toolbar). Then when you drag a pasted object, it will snap to the grid lines. So it isn't really like an "Align" function, but it works once you get used to it.
If an object isn't on a grid line (if it lies between two grid lines), then when you activate "Snap to Grid" and drag it, the object will snap to the next place on the grid in relation to where it is between the two grid lines, instead of snapping to a grid line.