if you can separate the newel from the banister, it will be easier when getting it back in because if you locate the bottom onto a peg/dowel the top off the post will be perhaps 4 or 5 mm higher because off the angle and you will probably have to shave a wedge to allow the drop through an ark if yo take this off the ceiling within the path and footprint off the post you wont see it
although looking at the picture the pocket on the wall side may be quite loose and filler used but my idea is easy removal with little or no attention to decoration to allow easy safe use