We upgraded to the Editor 2.0
However I can't seem to find where to store the module codes.
I miss a "Module" section within the Design Studio.
Am I looking in the wrong place?
There is no such thing as a module library. Modules are email templates sections and have to sit in an email template.
Look at Marketo starter templates, they are full of modules . If you create an email based on one of these, you can click the "edit code" button that will give you access to the code.
Unfortunetly you can not pick and choose modules from different email templates. What you would need to do is have a master template that has all of the modules you could possibly use and then you just drag out the ones you require each time you are building an email.
You could try and reduce the template by breaking it up a little bit. For instance if there are modules that will only be used for events then create an event template that has those, theres no need for them to be in the normal template.
I hope that makes sense. Jenna Molby created a great blog post on creating templates which might be worth a read http://jennamolby.com/how-to-create-marketo-2-0-email-templates/