Synth-tree viewer: comments and properties should stay closed (or open)

[jimallman]

As mentioned in this Feedback issue, some uers are annoyed by the persistent re-appearance of the Properties window after they've hidden them once.

If I want to hide the properties, I want them hidden. I most certainly do not want to have to hide them every time I move through the tree.

The current behavior was chosen out of concern that a new user (esp. in a narrow view like a tablet) would always see meaningful data, beyond just the tree structure. This has come at the expense of other users who want to move through the tree without the clutter.

We should remember this choice (in session? in browser History state?) and maintain it, at least during the current session.