When reordering pages, respect "folded" state of subtrees

[mamhoff]

Is your feature request related to a problem? Please describe.

With a large tree, and when moving large subtrees, it's UI-wise difficult to navigate the "Reorder pages" feature. If the tree view in that feature would remember which pages are folded, that would make things a lot easier.

Describe the solution you'd like

See above.

Describe alternatives you've considered

I think this solution is wonderful and haven't considered alternatives 😛

[tvdeyen]

Nice idea. Same solution already proposed by @robinboening in #1350

But, how do we allow to drag pages into folded pages? You simply can't I presume. I am fine with that. People could expand the sub tree first and then drag pages into it.

Like to PR this @mamhoff ?

[github-actions]

This issue has not seen any activity in a long time. If the issue descriped still exists in recent versions of Alchemy, please open a new issue or preferably open a PR with a fix. Thanks for reporting.