I know that LibreOffice Writer can facilitate subscripts and superscripts in ordinary, non-formula, text—when I copy and paste such things from Microsoft Office Word 2007 documents LibreOffice Writer manages to accommodate them. My LibreOffice Writer version is 3.6.4.
I haven't managed to find any better place to ask this question, if there is please direct me to it. I am running 12.10 if it is relevant.
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Keyboard Shortcut
As detailed on the LibreOffice help site:
For a GUI solution
Use Tools -> Customize... to open the following dialogue, then navigate as shown in the screenshot below:
Adding these will add them to the menu bars and thus give easy gui-based formatting, as opposed to a shortcut.
This works on my keyboard set to English (US, alt, intl.)
ralt + shift + . then 2 gets me ²
ralt + shift + , then 2 gets me ₂
and while I am at it:
compose + 2 then 3 gets me ⅔
This works in any application, including LibreOffice and the terminal.