Disable translation of custom taxonomies

No there is no special option. Just put the same value for all languages, this will essentially disable it.

How do you create custom taxonomy? In theory you may update i18n configuration to customize particular pages with custom taxonomies (https://qtranslatexteam.wordpress.com/integration/), but it is probably not worth of efforts?

Thanks John, I thought I should update the configuration i18n, but still I have to understand how it works, it can be useful for the integration of other plugins.

This would be a helpful feature. I use toolset (wp-types) to create custom taxonomies, and the Admin display shows the unparsed qtranslate code in the Admin Column, which is not ideal.