To get a unique id for a content item, you simply use {{id}}, in the template part of the visualizer editor.

For example:

<article class="news-headline" id="{{id}}">

It’ll come out as something like:

<article class="news-headline" id="aa1a93b2-cca4-4a32-bc0a-2c52a1b28019">

If you need to link to it, e.g. for a Bootstrap modal, use something like this:

<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#{{id}}">

It comes out like:

<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#aa1a93b2-cca4-4a32-bc0a-2c52a1b28019">

The ID is tied to the specific content item, so you can use it across multiple visualizers (e.g. put all the buttons in one visualizer, and all the modals into another one).

This might seem obvious, but I didn’t find it in the documentation.