My Takara-nishiki has a growth that seems to be developing inner stripe variegation, is there a name for this? It is not super strong and new growths from it have been mostly green.
We will see if it reverts to some other variegation or looses it entirely. This is one of my favorite Neos and has proved to be a great grower/bloomer.
Takaranishiki that has shifted to inner stripe (naka-fu) is called Takaranishiki-Nakafu 宝錦中斑 by most of the sources I can find at the moment. There is one source that abbreviates it to Takara-Nakafu 宝中斑 as well.
From the photos of Takaranishiki-Nakafu I've found they look very similar to your inner stripe growth:
If you eventually choose to divide off this growth and grow it separately, I suggest growing it in higher light. Inner stripe varieties of this type show stronger variegation when grown brighter.