Superscript is more of a display standard, I would advise against it in the actual tiddler titles. Try using captions or by manipulating titles as they are displayed in lists, but not the actual title.
If you really want tiddler titles to appear that way you could update the way the viewtemplate renders them, perhaps when a tiddler has a tag, a class or even an alt-title that includes the supperscript and apply that.
Perhaps you could explain your motivation.
Tony

It's of course slightly slower to fetch your desired characters from lists such as https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts than typing them out using common characters in KaTeX but should you need to use superscripts and subscripts quite regularly, using a text expander such as PhraseExpress would be a worthwhile solution (eg., 2sup → ²).