If I may, I'd like to suggest few modifications to the UI:
1. Some of the fields are a dark-grey on a light-gray background, (i.e. "Not") and are in relatively small letters. Changing it to something with higher contrast and increasing their size may look better. Mouse-over does improve situation marginally, but not enough IMHO.
2. The individual filter fields are pretty large, relative to the information payload in each, forcing to scroll up and down more than warranted in a simple queries. May be adding "+" and "-" for appending or removing filters and reusing the rest of the same horizontal space will yield higher density.
3. Actual output on top is not immediately apparent and is too close to the separating line under it. Perhaps few more pixels in between and a code box will do some good.
4. The "Highlight Command" icon under it could be moved to the very right of the output, to be more aligned with other tools using same approach (as seen in Azure, for instance).
5. Instead of "highlight command", possibly "Copy"
6. Possibly adding "History" drop-down, to retrieve the commands and editable filters for modification and reuse.
7. Possibly adding "Favorites" tree with subsets with same functionality as "History".
8. Inverse process: paste command to generate filtered steps.
Sorry for being picky, but it is a great tool and I'd like to see it evolving in even a better one.