Fix arrows at the bottom (wrong hierarchy) introduced in MR 760

Left and Right arrows were added to fix #2081 (closed), but the hierarchy in MR !761 (merged) was wrong, and the arrows were shown at the bottom, see #2081 (comment 1414935).

This MR fixes the hierarchy, so the arrows are shown in the correct position.

I should have tested locally, but thought wrongly that building a local instance of Nautilus would be hard to set up and very slow to build. But it is actually quite easy to install the Builder tool, and building is fast.

Arrows in correct position (from Builder)