[Zope] problems creating a Contents management tab

[Bob Shelton]

> As a little reminder when working with tabs.
> They sometimes don't show if there's an error in the action value.
> I've a few times hacked the tabs of folders or products and extended them
> with my own classes. If my classes fail startup, the tabs just don't appear.
> Be careful.

is there no straightforward way?
where exactly is the code to the contents tab of ObjectManager?

thanks.

-bob