Evernote is fine, but its text editor is strange and not good for storing code snippets. The fact that is allows HTML but can only manipulate a subset of HTML is a bit frustrating.
Is there any way to edit Evernote  snippets outside of Evernote?
My first read thru suggests this:
Copy and Paste the Evernote text into TextEdit, or another editor of your choice.  Clean it up, modify it to your pleasure…  Then Copy & Paste it back into Evernote.
But I maybe misunderstanding your question… Â Do you mean to edit the Evernote data without using Evernote? Â The data is stored in ~\Library\Application Support\Evernote
The Evernote.sql file is presumably the SQL database that stores the tags, sync information, etc…
The Content folder is broken up into individual folders, in my case, marked PXX where XX is a number… Â Inside each folder is an filename.ENML, filename.html, & thumbnail files.
The ENML appears to be an XML file with the contents of the note. Â The content.html appears to be a straight HTML file of the content, and the thumbnail files are thumbnail views…
I modified the XML file, and the evernote client did not see the changes… Â So I presume you can modify the data, but without reverse engineering the database, you can’t force the client to sync the changed data….