There are several ways to do this.
In the MTEXT editor write the index text as a stacked text - e.g. 2nd/xx hole (if you have AutoStack disabled, select the text to stack - nd/xx, right click and choose 'Stack'). Select the stacked text, right click and choose 'Stack Properties'. Delete nominator or denominator of the stack (e.g. xx). Set the 'Style' to 'Tolerance'. (gives: 2nd hole)
If you are using a font with full Unicode set, you can also use Unicode characters for "2-superscript" - \U+00B2 or "3-superscript" - \U+00B3 or "2-subscript" - \U+2082, to form single-line texts like E=mc2 or H2O. This approach can be used even in plain Text (not MText) entities, dimensions and labels.
If you are using an external Mtext editor (not Internal), you can also use the MText control characters - e.g.: