I see what you are trying to achieve. I thought through it, looked at the code, but I see no good solution, because there are some problems:
– If the user enters the keywords in different order like “anglais isabelle”, then the search would look in the wrong fields, because there is no way to distinguish the meaning of each word for the search.
– If the user enters more keywords, then what would happen with the rest? “isabelle rose anglais” for example. The problem is almost the same, it's hard to tell which field to look where for a program.
The keyword logic is exclusive for each field, thus probably the best solution for you is to change it to “OR with exact keyword matches”. That way each word individually is compared to each field.
However the next update will have something that might solve this for you – dropdowns and radio buttons from custom fields on the settings dropdown. In your case for example you will be able to create a dropdown or radio field with languages.Best,
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