spanner creation is inconsistent between shortcuts and palette.
Currently, pressing '<' is a very convenient shortcut for creating a hairpin. It puts it in the default location and spans it over the current selection (if there is one).
Double-clicking a hairpin in the palette is a far more discoverable method for new users, and it should allow the same conveniences. Currently double-clicking doesn't work at all; the element has to be dragged.
Obviously this applies not only to hairpins, but to any spanners in the palette.