There won't be an automatic snap grid point in the centre of symbols. The snap grid has it's origin in the origin point, the very point you are attempting to move, and you wanted to move it because it was at the edge and not the center of the symbol to begin width. If the origin is at the edge, there will only be a snap point in the center if it so happens that the distance to the center of the symbol aligns perfectly with the grid size which is just a luck thing. Snap grids are after all calculated as a fixed grid starting in the origin, not magically associated with the image. As Sue says, you'll have to judge by eye.

No file. The default colors are hard-coded into the software.

Yes, with presets, you must apply them manually to each map. But the advantage it that it can be done with existing maps, and not just with apply to new maps.

@jmabbott the issue with that scheme is that it makes it easier IF you know exactly when the style was from, but if you are looking for a style by name, it is a huge unsortable mess making styles much harder to find. It may make sense as you are following along the current year, but whenever you wanted a style from an earlier annual, it would be much harder to find.

Personally, I usually never remember when I style came out, but I usually know the exact/approximate name of it.

Obviously, the new map dialog could be better, it was written at a time when we only had a handful of styles, but until we get a better one, my vote at least goes to sort it by the most important part, the actual name of the style and not some prefix. (I am not much a fan of the "Annual" prefix either)