Create another rule on top of the first that will be an exclusion rule. Separate window titles with |. So for ex conky|pqiv|plasmashell|something should be placed in the Window Class while having Regexp instead of Unimportant. For this one force the opacity to 100%. In case you don't know what window class something has (tho it is usually in the titlebar) you can press ALT+F3 → → and get the window class or when you create a rule there is a button that will let you click on something to get its properties (detect window properties).The end result will look like so, and can be imported by saving it as .kwinrule.