some progress on the filter tab, various changes

core.lua

@@ -406,4 +406,16 @@ function Aux.item_quality_index(item_quality)
             return i
         end
     end
+end
+
+function Aux.hide_elements(elements)
+    for _, element in pairs(elements) do
+        element:Hide()
+    end
+end
+
+function Aux.show_elements(elements)
+    for _, element in pairs(elements) do
+        element:Show()
+    end
 end