Alright, added it! Submitted v1.8.16 to the asset store, and it's already live on itch.
I added a <y=float> tag that can be used to set the y offset of text, and in addition to this I added <sup> and <sub> for superscript and subscript. What these tags do is essentially the same as typing <s=0.5><y=0.5>, except it uses values that you can set withing the TextData Inspector, under "Master". </sub> or </sup> will also cancel size tags, so another should be typed afterwards. if you were already using one, STM has HTML-like tags, but they don't "stack" in the same way as HTML tags...
Can't believe I forgot to add this, thanks for pointing it out!