How to get the status of the plug-in

I want to make a judgment based on the status of the plugin, but I don’t know how to get the status of the plugin。

I’m developing plugins for the first time。 I found that the most convenient way was to read someone else’s source program, and it was difficult to find the methods and properties I wanted in the documentation。It makes me feel inefficient。
I don’t know how to quickly find the methods and properties you want,Could you tell me how to solve this problem? thanks

The hub has collected all the resources here:

thanks.