In short, normally! As if they were in the same tab.

I never liked inner classes, this just reinforces that dislike.  It looks like I'm calling methods within the inner class, but they are actually defined in the main class.  Yuck.

Hello!

This has not to do with tabs but with the nested classes , but
yes, you can refer to a PApplet object from a nested class.

Just declare a global var in setup(), set it to "this" and use it in any class you like.

So in setup():

1. thisVarPointsToMainClass = this;

in any class instead of "this" just use "thisVarPointsToMainClass".

I know, it's not beautiful but it works.


Alternatively
Alternatively you can pass "this" as a parameter to the constructor (or even method?) of the class
and store it there. Then you avoid a strange global var...


Greetings, Chrisir    

If I am not mistaken, this second question is answered in the article Why I can't create an instance of a library from my own classes?
As said by Chrisir, I just realize... Well, it is an opportunity to remind it is a Technical FAQ.