It used to be that you held shift to rotate things and they would snap to 45degree angles, you could hold control and shift to fine place and fine rotate and (atleast in our client) you could hold alt to walk around while still having the blueprint on your mouse.
This mean that if you were placing a stockpile you should hold shift to place pile and fill it up in a grid-snapped position. However now shift does fine rotate and placement, so nothing ever snaps to grid when placing stockpiles, which is super annoying.
And if you are holding control when you click then you just walk to the spot instead of actually putting the building sign down. I don't really know what the reason behind these changes were but it feels like a massive regression imo.