You wouldn't necessarily have to show the private images. But maybe you could make up examples of a problem, if it's requested. In this case, I'm not sure if an example is needed. Unless we have not understood your questions.
In Inkscape, the point 0,0 is at the bottom, left corner of the page. If you need to move an object from one place, to the center of another object, there are at least a couple of ways to go about it.
1 - With snapping properly configured, you can snap the center of one object to the center of another (or the rotation centers, which is sometimes different point from center of object)(I can't explain why, because I don't understand it myself -- it just is) Although with that technique, it will be hard to know the coordinates of that center point.
2 - Do some math and change the X and Y values on the Selection tool control bar. Then do some more math to figure the center of the objects.
3 - Use a grid or guides to help with placement.
4 - Use Align and Distribut dialog in certain cases. Although again, determining the center coordinates could be difficult.
... well what are the coordinates from the center? Well I can't really tell, can I, since they are representative of the bottom left edge!
You may want to get into the habit of using a pixel grid. Then you can use snapping, to snap the center (or rotation center) of objects to whole pixel values. I'm not sure if your canvases are usually quite complex or simple. If they're quite simple, perhaps guides would be better then grids. (Inkscape does have an axonomic/isometric grid, by the way). (Also, guides can be rotated....although if the center point is the main goal, I guess it doesn't matter at what angle the guides lie.)
Anyway, with a pixel grid, you can easily know the center coordinates.
Out of curiosity, why do you need to know the center coordinates (if it's not private information)?
Oh, just re-read your op. For your question #1 - I think it's probably hard coded. I've never heard of anyone changing it..... It goes to the very core of how Inkscape works, to my understanding. So no, it can't be reconfigured.
For your question #2 - Once we understand what's happening on your canvas, we can help you configure snapping. Here's the manual info, if that could be helpful:
http://tavmjong.free.fr/INKSCAPE/MANUAL ... pping.html However note that there were some changes with the new version 0.91 and the manual hasn't been updated yet. But tell us what you are snapping to the guides (or snapping the guides to) and we can advise.
For your #3 - Please tell us the exact steps you're taking.
The simplest way to make an easily editable drop shadow:
-- duplicate the object
-- move to the bottom in z-order (Selection tool control bar button, or Object menu > Move to bottom)
-- since the object is on the bottom, it's hard to drag, so I usually use the arrow keys and move the object down and either left or right (depeding on light source) -- each tap of an arrow key moves the object by 2 px (Shift + key press moves by 20 px, and Alt + key press moves tiny amount - can be changed in preferences, if you like)
-- Object menu > Fill and Stroke > Fill tab > Blur (near bottom of dialog) There are much more complex ways to make a drop shadow, using more complex filters, from the filters menu. For those, you may want to read up on filters
http://tavmjong.free.fr/INKSCAPE/MANUAL ... icUse.html and
http://tavmjong.free.fr/INKSCAPE/MANUAL ... reset.html-- if you need to also change transparency, you can either change the alpha value of the individual color (Fill and Stroke dialog) or you can change the opacity of a whole object (no matter how many colors) using Opacity slider, which is just below Blur. (If you used a filter to create the drop shadow, you will not be able to edit it with the controls in Fill and Stroke dialog - only with Filter Editor - with details, we can help explain how)