A straight segment that already has a head on its far end.
The Arrow is the same markup as the Line, with one difference: its far end starts with an open arrowhead. Everything else behaves identically.
Draw it: press at the tail, drag to whatever is being pointed at, release. The head lands on the end you release at, so drag towards the target.
Identical to the Line: Thickness 1 to 20 default 2, colour, opacity, and the same nine ending styles on either end. The only difference is the default, an open arrow on the end rather than nothing.
For a leader that curves around something before it points, use Arc: its head follows the curve's direction at the end, so it still points at its target rather than along its chord.