Cloze images = Image Occlusion is part of Anki or has to be added via an add-on?

I have anki running on a chromebook linux partition and this is what I get - I don’t see the button to invoke the window for cloze image=image occlusion, where I can put masks over the words in the image.

Image occlusions are not a native feature of Anki as of today.

There are several add-ons for this, the most popular and feature-rich being Image Occlusion Enhanced for Anki 2.1 (alpha) - AnkiWeb.

Closet For Anki - AnkiWeb is a great option for people who want to reduce the amount of notetypes for their workflow, but it requires some effort to set up.