Clicking on the Select All button selects hidden

I got your point.

I will modify the All, Not Used, Used and Missing buttons to only act on the terms visible in the list (after filtered by the category and the search textbox).
So that it be more intuitive.

The previous behavior can still happen if you select "everything" as the category and clear the textbox. In that case, all terms will be shown in the list, and then all buttons will select based on.

Thanks for the suggestion,
Frank