How can I access code to adjust elements of a web app that the basic interface does not allow you to adjust?

[Bianca]

I'm looking for a simple way to have more control over my web apps. I installed Web AppBuilder Developer Edition thinking this would give me that control. From what I can tell with Developer Edition, it allows you to develop your own custom widgets and themes, which you can then add to a map. This is great, but for now I just want to take an existing widget/theme on a map and go into the code to change some parameters like location, size, etc. without having to save a whole new widget or theme file. This applies to parameters that are not available to customize in the regular AppBuilder. Is it possible to do this with Developer Edition? If not, do I need to use ArcGIS API for JavaScript? I don't want to start from scratch. Ideally I could use AppBuilder to start a web app and then have access to code to adjust elements.

[spanton]

I believe I have a similar question.  I've created a webapp in WAB and would like to access the JS in order to add some additional functionality to the app but I cannot for the life of me find where the JS is. I pulled the created webapp into WAB Developer Edition and I can see the three .js files referenced within the .html file (env.js, simpleLoader,js and init.js) but I'm not sure any of them are what I'm looking for.