Are similar items in the bags on all these reliefs?
Of course I don't know what these represent but I suspect the Pine Cone looking item symbolizes unfolding knowledge.
In ancient reliefs deities and kings always held items of power/status all would recognize in their time setting/area, like;
a staff or mace, symbols of office/religion, drug paraphernalia.
In all seriousness it may be the drug paraphernalia option.
Chemical mysticism, Ayahuasca/Ibogaine/Opiates can gain one access to the spiritual realm, a source of power/status.
Answers we may have to wait for.
I wonder if any have been dug up but go unrecognized.
To spot one mis-identified on some museum backroom shelf.
Now that would be cool to do!