May I append one ADF to another?
According to the docs:
Depending on your settings, you can learn a new area or append to an existing ADF.
Right now, The API doesn't provide any functions for merging two or more ADFs to one. But you can append the new area's description to an existing ADF by Enable ADF : "Learning mode" and "Load ADF" mode
Check: https://developers.google.com/project-tango/overview/area-learning on "Using Learning Mode and loaded Area Description Files part"
The last one is the condition I mentioned. Also, in order to successfully append new area's description to an existing ADF, application must be localized to the existing ADF first. Then you can start learning the new area. In the end don't forget to save the new ADF, which is saved as the same uuid.
Updated: On the recent release. Append existing ADF will save as a new UUID. The new ADF area will cover your new area and the previous existing ADF.
You're outside the scope of what the system is currently capable of - you can create a new ADF or you can add additional information to an existing one, but the system doesn't have any facilities for merging smaller ADFs into a larger master ADF and there isn't enough documentation to hazard a hack