Using x and y coordinates and temporary guide lines are all valid CAD techniques. Hint, put your pointer on your reference point and press the space bar to zero the relative coordinates (the dx, dy coordinates). I find this works better on the legacy canvas as the pointer doesn’t snap to the grid on the OpenGL canvas for me unless I’m actively moving or drawing.
Also, for aligning parts, yes there is this function (I’m on the v4.0.6 stable on Win64) in the OpenGL canvas. You want to select multiple parts (either drag selecting or shift-clicking on the parts you want selected) and then right-click. You should see an “Align/Distribute” sub menu. It doesn’t have aligning by middle or center, but it does have aligning to top, bottom, left, and right. It also allows you to distribute the selected parts horizontally and vertically.
Hope this helps.