Duplicate selection on drag

There are just a few things I like from propietary vector graphics software but there is one from a famous one that is super handy and that when you don't have it you miss it, I know there are similar options in Inkscape but none of them are as easy, fast and "natural feeling" like the following: the ability to duplicate your selection by just using ALT + click + drag.

I'm adding the feature in the Inkscape way 😁 that is, I included it as a Selection Tools Modifier, which will be disabled by default so that it doesn't interfere with default Inkscape and with the option to bind the feature not to just to ALT key but to any other modifier key combination that the users wants to create and that matches their workflows. BTW, ALT key works great and doesn't interfere, but it changes slightly the normal behavior.

So, if enabled and set a modifier key, as already said, I suggest to use ALT to test it out as it is still compatible with normal Inkscape, because this is how the feature works in the other software and I bet users switching to Inkscape will feel it more natural.

Please, have a look at the following example and pay attention to the mouse and keystrokes used while dragging:

It's worth saying that in the way I found a bug and fixed it: when moving objects using the SELECT_FORCE_DRAG (or the new SELECT_DUPLICATE feature) and snapping ON, the selection wasn't really snapping to anything... Now it works as expected, either way, if you use default Inkscape, that is, with SELECT_FORCE_DRAG enabled and SELECT_DUPLICATE disabled or with both enabled 😁

I hope you like it