To my knowledge quicklook isnt built like FCP color corr. filter where you can apply it multiply times into the same clip.
The way it works is you save the 'looks' as many times you want(which is stored on the left side in the Looks window under 'Custom') This way you can apply multiple looks onto the same clip and go back to your custom saved looks and pick the one you want.
{To save a look; click on the "untitled look" box located at where all the look filters are kept in the middle section.}