Found while drawing some diagrams in FigJam: the UI to set the arrow end of a connector line mirrors the orientation of the line.

In this case, the start of the connector line is horizontal, and the end is vertical:

Here, both ends are vertical:

Not only that: the icons for the shapes also reflect the direction of the connector line, so the arrows will be pointing up if the connector is also pointing up:

This level of attention to detail is a testament to a team’s design skills and love for craft. But when it comes from a big company like Figma, it also tells a lot about their design culture.