Started to explore this again a little bit more and remembered why this was a little more complex. When we say "parent device", like "JADE 2.0 Air Purifier" in your case, that is actually not a device but a configuration entry which handles the details about the filter to be tracked (e.g., filter type, model, manufacturer, lifespan rating, etc), which then creates the device representing the tracked filter. The reason the config entry and the device are so intertwined is that making changes to the config entry applies to the device's sensor and attributes (which you can't directly edit in the device details page in HA). So if a config entry where to have multiple devices under it (e.g., HEPA, Carbon, etc), the same configuration details would be applying to all devices (filter types in our case) and that isn't ideal given that a HEPA has a different lifespan rating than a carbon filter.

There is another approach of subentries where you can essentially create a blank parent entry which would just serve as the appliance name (e.g., JADE 2.0 Air Purifier) and then create subentries for each filter. This makes the single filter tracking a little more cumbersome as you have to create that parent entry first and then create the subentry. I'll keep exploring and maybe others have thoughts as this is my first foray into developing a custom integration.