I would also like to know how this is done. I only know of one person, maleo, successfully creating a mode. He created a debug mode...

3. The name can be probably anything, like for libraries. But the jar inside the mode folder should probably have the same name than the above folder. Same rule as for libraries, likely.
I haven't tried to create a mode. What kind of mode are you trying to do?

Hey, you can take a look at this mode template that Martin (maleo) made.

https://github.com/martinleopold/TemplateMode

Awesome! Thanks - unfortunately it doesn't seem to let Processing load when these modes are installed. I'll keep researching!

Because the ADK requires a bit of extras in the manifest which aren't currently added by Processing as far as I know or can see. (disputable I know, but if you want to be proper you need to add them)

There's the tool available on arduino.cc, but that's a massive hack so I wanted to release it as a mode instead until Fry and company have had the time to add ADK support (which I guess is low prio right now).

Has there been any progress in this area?  I'm thinking about building an extension, and trying to decide between Library and Tool - which seem to be fairly well documented - or building it as a new Mode.