I know that this is for searching. But you don't get the point. You have attributes, like Date, Category, Subject. Each attribute can either contain arbitrary text (like the subject), or one of a set of predefined values. So category can be, let's day, "one", "two", "three". You define the possible options of the category with

Options Category = one, two, three

If you then define the quick filter

Quick filter = Category

then you get for the category a drop-down box where you can select "one", "two" or "three". If you do so, elog shows all logbook entries where the category attribute has the selected value.

I hope that this is clearer now.