@Kimya_Gandhi and @robkeller mentioned the same about zerowidthjoiner and zerowidthnonjoiner for Devanagari. Microsoft applications may expect them to be present in the Devanagari font file if I understand correctly.
So, I guess they ought to be in the language sidebars, right? Technically, they all are categorised as Separator. So I see either a new subcategory Separator, or we squeeze them into Other. I have a small tendency to the latter because it is just a few glyphs.
I see Myanmar has a Separator subcategory already. I guess it is better to add that everywhere then. And possibly review the Other subcategories, because sometimes they contain just numerals, and that should be named in a better way.