After launching the New firmware library manager for Particle Library 2.0 and managing my private libraries in command line with particle-cli 1.19.1 utility I have detected some drawbacks that will be hopefully resolved in next versions of that utility and documentation as well:
particle help libraryends with error “Potentially unhandled rejection  TypeError: Cannot read property ‘does’ of undefined…”
There is no command
particle library validate, which is mentioned and recommended in the example library https://github.com/spark/uber-library-example README.md.
There is no command in particle-cli for removing private library, or not that feature documented at least.
After migration an existing library to version 2.0, the subfolder src/library-name with additional header file is created, which references to the original header file, probably for backward compatibility with former way of referencing libraries in applications. However, the particle-cli fails at example flashing in the command
particle library flash <my_device> examples/<example_name>, because it includes both header files and that additional one is considered as the original one at original folder position with reference to the upper folder, which is outside of the library. For the time being that additional folder has to be removed in order to flash example to fimware from command line successfully.
The compiler considers the 32-bit data type “word” as unknown now, maybe due to compatibility with 8-bit Arduino platform. However, this data type is still present as a legal data type in the firmware reference documentation.