This video is short but extremely important for understanding why deformers sometimes seem to forget what drawing swaps they belong with. From my understanding, Harmony uses the terms "transformation chains" and "deformation chains" interchangeably. They're the same thing. In this video, I also explain the importance of clicking the "plus" button (Create New Deformation Chain) in the deformer toolbar so that Harmony will automatically set up the Transformation-Switch and add the names of your drawing swaps to the switch.
If you'd like to see the problems you run into if you forget to click the "plus" button, watch from about the 20 minute mark of this video:
Manually adding the Transformation Switch for Multiple Deformation Chains: • 06e Swaps- Blinks and ...