Actually it seems not possible to set in a multi-language installation for a particular secondary language globally to a “draft” state in order to not to be displayed in the front-end. Thus the suggestion is:
add a “state” variable to the language definition with values “draft”; “published”.
all collection types do not show a particular language for the front-end, if the global “state” variable is set to “draft”.
all collection types do show a particualre langanguage for the front-entd, if the “state” variable is set to “published” (default).