Thanks for your time, Dr. Sassi. So I've contacted Tech-Support, here is the answer:

This problem has been confirmed as bug connected to layers. It happens, as soon as at least one of the selected objects is part of a layer. Without using layers, the shortcuts work properly. Our developer is aware of the issue and I hope this can be fixed soon.

In case anyone else has this issue, for me, the problem was the CVtoolbox plugins; there was "CV-Active layer" enabled, and every newly created object was assigned to default layer.

Hi. I'm trying to create multiple separate parent objects (e.g., Nulls) for several selected cubes.
When more than one object is selected in the Object Manager, holding Alt and clicking the Null icon does nothing. Shift+Click and other modifier keys also don't work.
This used to work in previous versions: selecting multiple objects and Alt+Clicking a parent object (like Null) would create one individual parent for each selected object.
Is this a bug in Cinema 4D 2026.1.0, or am I doing something wrong?