So there is a shortcut to create a new layer Command + Option + N.
When this new layer is created, it is also selected. Any shape i create at this point will be added as a child to this newly created layer. So its sole purpose seems to be a group. I believe people who create a new group or layer have a very specific thing in mind and want to give this logical group a name.
Please look how Apple does this in the Finder: Command + Shift + N creates a new folder and also enters edit mode with the text already selected. (also Return enters edit mode)
I think Affinity Designer should at least have this behavior as minimum requirement and also add a shortcut.
There is a shortcuts panel in the settings where you can even choose the layers menu to manage shortcuts but there is a menu item missing: "Rename layer".
Again comparing it to Finder:
Command + Shift + N -> New Folder with preselected name ready for typing while both hands are on the keyboard.
Pressing the enter key: Starts and stops edit mode.
Affinity Designer:
Command + Option + N -> New Layer and does not preselect the name for me so I have to reach for the mouse, move the arrow to the layer and click on it only to then reach back to the Keyboard.
Pressing the enter key: Computer makes Beep.