This is an add-on for Blender 2.80+.
It adds a widget that lets you quickly manage the visibility of your collections, similar to the layers widget of Blender 2.79.
Clicking on a button will toggle the visibility of that collection, and you can hold Shift and click-drag to toggle multiple collections at once. Each button represents a collection in the order they were created.
I updated this add-on to version 0.9.2. It supports Blender 2.80+ (including 2.90):
Made the cells a bit wider so they look better on the UI.
Added a feature to the “Toggle Visibility” button: if you Ctrl+Click on it, not only will it toggle the visibility of all collections but of all scene objects as well.