an alternative is the same letter in a different form as “a” and “ɑ” (a.alt). An alternate must be manually selected by the user.
I think you mean a ligature. Then a different symbol is automatically created from a string. (In your case it is qq.liga in Fontself). To make this automatic, this option must also be activated in the writing program.
WORD: OpenType ligatures aren’t enabled by default, though.
To enable OpenType ligatures, right-click on some text, select Font, select the Advanced tab, and select Standard Only from the Ligatures combo box. This enables the standard ligatures, like fi and ffi.
P.S. If you are interested in European special characters, I wrote a long article about it. It is also a basis for creating fonts that should have more than just 2 x 26 letters: http://www.computergrafik-know-how.de/wp-content/uploads/2021/07/A048-FD-European_Special_Characters_opt.pdf