TYPO3 Core

It also happens when you edit page properties and save them (I assume it probably triggers the "reload page tree" function)

I think this "bug" comes with the new svg pagetree.
"bug" because its more a missing feature of the new tree.
In the old extjs version there was a lastSelectedNode property came from the stateHash array.

From the UX and accessibilty perspective, this is really bad.

[UPDATE]
After some research I found out that the web component of the page tree basically allows to set the active state via the JSON supplied by the TreeController.
The only missing thing in the pagesToFlatArray method is to set $item['checked'] of the last selected node to true.

Unfortunately I did not found any simple way to get this info at this place.
Maybe it has first to be stored somewhere in the user session?

As far as i see, there are three problems at the moment:

1. The current selected page is not stored in the backend user session to carry this information to e.g. the TreeController
2. The selected page item does not get the property 'checked' = true inside TreeController ajax return, produced by its pagesToFlatArray method
3. The pagetree does not get a refresh trigger to fetch a possible updated checked state

Here are some thoughts, how to fix it:

Take the current selected pageId inside eg. the SiteResolver middleware and store it inside the backend user session like so:

if (array_key_exists('id', $request->getQueryParams())) {
    $GLOBALS['BE_USER']->setAndSaveSessionData('lastSelectedPage', $pageId);
}

if ((int)$item['identifier'] === $backendUser->getSessionData('lastSelectedPage')) {
    $item['checked'] = true;
}

To trigger the refresh of the navigation, I'm currently not sure of the best way.

I think the PageLayoutController::renderContent method would be a good place to add something like this:

if ($this->id !== $this->getBackendUser()->getSessionData('lastSelectedPage')) {
    $this->pageRenderer->addJsInlineCode('refreshPageTree', "top.document.dispatchEvent(new CustomEvent('typo3:pagetree:refresh'))");
}

Another idea is to add something like Tymoteusz Motylewski mentioned in https://forge.typo3.org/issues/92745

He talk about a JS API for the page tree, with a "selectNode" method.

Patch set 2 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/81300

Patch set 3 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/81300

Another issue that is probably related: If I create a new translation to a page, the page tree gets reloaded but the page that I translated from is no longer highlighted in the tree. That makes it hard to remember, which page is now getting translated, if you bulk-operate on a lot of pages.