Left navigation not respecting hidden toctree

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I work on the Blender Manual and about 2 years ago, we switched to using the Furo theme. This week, I noticed that one of our pages (https://projects.blender.org/blender/blender-manual/raw/branch/main/manual/getting_started/installing/index.rst) lists a page in a hidden toctree at the very bottom of the page.

This is done to prevent Sphinx from complaining about pages not referenced in a toctree.

However, browsing the created HTML produced by Sphinx shows that the item appears in the left navigation tree even though it is set to hidden. You can see it here (https://docs.blender.org/manual/en/dev/getting_started/installing/index.html).