The 3.0 spec really want you have the Core tree expanded

[licquia]

From the 2024-05-07 tech call (ref @kestewart ):

When the 3.0 spec is opened, it centers the sidebar on the Core portion of the model, and expands the tree. You can collapse the tree, but under a number of circumstances, something feels it's important to re-expand the Core tree.

This makes the sidebar more difficult to use, as the Core tree is large, and it tends to make the actual current context scroll off the bottom.

[bact]

It could be something to do with the focus or "highlighted" position as well.

See some investigations here #939 (comment)

[bact]

We may need to set collapse_navigation: true in mkdocs.yml.
But from the documentation, this value is already true by default.