Clearing out the filter that you just created is very simple, but it is important to do because once a filter is set on a GPO, it tends to stick around until you manually turn it off. For example, I closed GPME after I was done poking around inside my Notepad+Calc policy, and then re-edited that GPO. Once opened, I was still only seeing bits and pieces of the policy, until I realized that my filter was still enabled even though I had exited and come back into that policy.

To clear your search results filter within a GPO, simply right-click on the Administrative Templates folder that you have filtered, and deselect the Filter On option:

If you need to re-enable your filter, do the opposite. Rechecking the Filter On option immediately turns the filter back on. It remembers your last filter criteria from the Filter Options screen, so there is no need to resubmit that criteria.