How are you managing reusable code snippets and code notes?

You can't go wrong with https://gist.github.com/ (you can even add code directly to a Gist from IDE's like WebStorm), and maybe a dedicated Slack channel where you share all these gists. Gist by the way has full version control capabilities like any file on GitHub, so you can update your scripts and keep track of the changes.

I've got both VIM and VS Code set up to handle common snippets, including snippets with certain parts that change (i.e., snippet variables).

If I need to share with others, I use a gist or just send it via chat. I haven't ever wanted to document a snippet itself since the all the source code is in git (and mostly documented) already.

What issues in your workflow are leading you to ask this question?

Well, from my experience when you are a part of a small dev team (like 2 people) you can use the Slack channel. Also, most of the snippets will be in your priv messages :D
From my experience, when you are a part of a bigger team (>2), the best place is the one where everyone has access and doesn't need to know another tool.
In my team, we are using https://guides.github.com/features/wikis/ because everyone knows the Github and it's the tool that we use already.
But keep in mind that the biggest issue to manage the reusable code snippets is that someone has to have goodwill to document these short instructions XD

Evernote is good for this.

Like @herval I'm not sure what you mean by managing code snippets, but for notes I use Trello which is where my tickets are and notes and comments are related to them.

Why do you need to “manage code snippets”?

Alfred