i've changed in section "categories / sub-categories" in the panel control K2. Item ordering: Title Alphabetical. I can change and save this part.
But i've changed in Main menu > Products > Item ordering: Title Alphabetical and this can't save. This persist Item ordering: Ordering. I don't want ordering, but I can't change and save to Title Alphabetical.

This is bug?

If this menu is a single category menu, then you need to set this in the category's settings.

I don't understand... Please, see this image
imgur.com/a/FYCZq

i've tried to change Title Alphabetical, but this doesn't save....

Unica categoria means single category. This option is for a single category, try the options bellow which are for multi-category menu items.

Thank you very much for your patience. I resolve this problem.
Put one category and I can change and save to Title Alphabetical.

You 're welcome :)