Art wrote:
"I am not saying that displacement current travels in the center but I
ask those educated in this field if displacement current has been
observed, measured and is present Beyond Doubt?"

Yes.

Displacement current is proportional to the rate of change of the
electric field. It moves at right angles to the direction of
propagstion.

Like charges repel without electrical conduction so a capacitor passes
ac while blocking dc.

A standing wave antenna stores energy in the magnetic field near its
center during one half of the cycle and in the electric fields near its
ends during the other half cycle.

Dielectric displacement is the electrical strain which occurs in a
dielectric medium when an electric field is applied. It is analogous to
the magnetic flux density and is expressed in charge per unit area or
coulombs per aquare meter.

J.C. Maxwell speculated displacement current produces magnetic lines of
force same as conduction current does, therefore an alternating magnetic
field would produce an alternating electric field and so on ad
infinitum. This was the key to electromagnetic radiation. Hertz later
proved Maxwell correct in the laboratory.

Best regards, Richard Harrison, KB5WZI