Can't move items with ruler

This demo shows the ability to move items with the ruler tool

https://wiki.bambulab.com/en/software/bambu-studio/release/release-note-1-9-1#h-10-ported-and-improved-measurement-tools

However, when I try to use it, the X Y and Z boxes are always grayed out. I’ve tried with a new plate and as simple as selecting two parallel edges in two cubes. I’ve tried combining the cubes into an assembly but it just doesn’t work. Is there a step I’m missing?