Levko is already a diminutive, as it contains the masculine diminutive suffix
-ko (which is used in several Slavic languages):
https://en.wikipedia.org/wiki/Ukrainian_name (in English)
The same goes for Odarka, as it contains the feminine diminutive suffix
-ka. Despite this, there are at least three known diminutives of it: Odarya, Odaronka and Odarochka. This is according to the Ukrainian Wikipedia article about the name Dariya:
https://uk.wikipedia.org/wiki/%D0%94%D0%B0%D1%80%D1%96%D1%8F (in Ukrainian).
As for the other names:
• Maksym (this is the proper spelling,
not Maxim):
https://uk.wikipedia.org/wiki/%D0%9C%D0%B0%D0%BA%D1%81%D0%B8%D0%BC (in Ukrainian; mentions that Maksym has at least the following diminutives: Maks, Maksymko, Maksyuta, Maksyk, Makson)
• Svitlana:
http://kurufin.ru/html/Ukrainian/ukrainian_s.html (in Russian; mentions the following diminutives: Lana, Lanonka, Lanochka, Lanusya, Svitlanka, Svitlanochka, Svyeta and Svyetka)
• Valentyn:
http://kurufin.ru/html/Ukrainian/ukrainian_v.html (in Russian; lists Valechko, Valentynonko, Valentynochko, Valko, Valya and Valyk as diminutives for Valentyn)
I hope that helps. :) Oh, and you might also want to educate yourself on Slavic diminutive suffixes:
https://en.wikipedia.org/wiki/List_of_diminutives_by_language#Slavic_languages (in English; the Ukrainian ones aren't mentioned, but this should still be useful to you)
"It is no measure of health to be well-adjusted to a profoundly sick society." ~ Jiddu Krishnamurti (1895-1986)