Taking the initial letters of all given and perhaps also family names, one could form another name which could also act as a nick name, e.g.
Margareta Esther Trixy
Anne →
Meta. Too nerdy?
(The middle names were selectted rather randomly.)
Another method, which accidentally came true for my oldest, is to combine the first letters or syllable of the first name with the last one(s) of the middle name to get the nickname, e.g.
Natasha Martina →
Nana (or
Masha if switched).