You can make selected text superscript or subscript, then tweak the baseline of the text by small increments.
Select the text you want to make superscript or subscript.
Click the Style button near the top of the sidebar on the right.
If you don’t see a sidebar, or it doesn’t have a Style button, click
in the toolbar. If the text is in a text box, table, or shape, first click the Text tab at the top of the sidebar, then click the Style button.
In the Font section, click
, then choose Superscript or Subscript from the Baseline pop-up menu.
To adjust the placement, use the arrows to change the Baseline Shift value.