Internal links with only the first level break the tree navigation

[spaenleh]

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[spaenleh]

#774 adds the possibility for users to force-reload the page which resets the navigation and shows the expected folders.
It is not a very viable solution in the long term.

The root issue is the internal state that accessible-tree-view keeps. When we change the selected node in the tree and it does not exist, accessible-tree-view crashes.

We could replicate the layout of accessible tree view and get rid of it.

At some point we will anyways implement the new progress and navigation design from Martina (modal for the full tree) and simpler linear progress on the side.