VST plugs-in Effect

After Audacity updating to 2.1.0, the VST Effect has changed, how can I know how many tracks was opened in programming?
[VST2.4, Microsoft Visual Studio2012]

Please stop starting new topics about the same question.
Please refer to this topic: https://forum.audacityteam.org/t/the-development-about-vst-effect/38413/1

Topic locked.