This is a more question than an issue report.

With the new RouterViewConfiguration we can set sef url parent section in the following way:

$category = new RouterViewConfiguration('category');
... ...
$this->registerView($category);
$foo = new RouterViewConfiguration('foo');
$foo->setKey('id')->setParent($category, 'catid');
$this->registerView($foo);

Everything is fine.

But how can we setParent, depending on differenct cases? For example, the item foo can be accessed from different parent view "category" and "tag":
index.php?option=com_foo&view=foo&id=1&catid=1
index.php?option=com_foo&view=foo&id=1&tagid=1

We would like to:
if url parameter catid exists: $foo->setParent($category, 'catid');
if url parameter tagid exists: $foo->setParent($tag, 'tagid');

Is it possible in Joomla 4? In Joomla 3 we can do it easily.
PS: Here we don't care about the advantage of SEO unique URL etc.