What percentage of the universe is non-observable?
As of now, this percentage is indeterminate.
If the limits of the observable universe are the limits of the holistic whole of the universe, the percentage of non-observable universe is zero.
If there exist a mirror-image-like another universe, the percentage is 100.
If the holistic whole of the universe is a multi-universe system of N universes, with N-1 other universes like observable universe, the percentage might be (N-1) X 100.
It is already a long wait for fixing the number of dimensions, in observable universe, as 5 (including time and temperature) or 6 or 7 or 8 or 9 or 10 or 11, If this fixing is deemed decisive, then there is a possibility of estimating the percentage of non-observable universe.