Ability to "pin" subgroups

I would like to be able to pin certain DOM APIs so that I don't have to scroll to find them within the top level DOM documentation. For instance, I would like to pin WebGL and have it show up as a top level item.

Start by reviewing how DOM documentation groups and subgroups are represented and displayed. Use the WebGL example to determine how a pinned subgroup would appear as a top-level item. Done means users can pin selected subgroups and find them without scrolling through the top-level DOM documentation.

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