Maybe I'm misunderstanding you, but normally, you'd have a name (namespace) for your extra (let's call it mycomponent) and put the objects in a category with the same name so they will be easy to find and store the files something like this:
core/components/mycomponent/elements/snippets/mysnippet.snippet.php
core/components/mycomponent/elements/chunks/myhunk.chunk.html
For files that need to be accessed via URL (e.g., CSS and JS), you'd do this:
assets/components/mycomponent/css/mycomponent.css
assets/components/mycomponent/js/mycomponent.js
Almost all MODX extras do it this way.
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PLEASE, PLEASE specify the version of MODX you are using.
MODX info for everyone:
http://bobsguides.com/modx.html