Thanks for your swift reply !
So, I made what you recommended, for both unique key value and search criteria setting (Simple Exact match ...), and now it works for radio button, with a unique alternative (Yes/No, On/Off), it means a unique value.
But I still cannot deal with multi-options (multiselect drop-down, multicheckbox).
The search only works with Search criteria sets on "Avanced ..." and option "contains one of". I guess because when I set search criteria on (Simple Exact match ...) values are not considered separately (English | Spanish | French) but as a whole thing [English,Spanish,French].
Is there any way to automatically set (embed) this type of search criteria (contains one of) on "multiselect" fields, whatever the global search criteria setting is ?
Perhaps I am asking for the moon
! But who knows ? Whatever .. it should work this way.