Universal search in UI is cool, and I’m all for it, but it shouldn’t be the only/primary way of accessing tools as tool discoverability is very low. The author tries to deal with this by putting the a menu next to a search bar and putting hints in the bottom menu (which I don’t think would really work here, as raster tools are less selection-specific than 3D tools). Search fixes the speed-of-access issue, but doesn’t help discoverability very much, as users still have to hunt through highly nested menus.
Looking at the screenshots here, I don’t think you actually need search to make those menus more manageable. One screenshot of current GIMP shows a menu tree that looks like “filter->render->noise->solid noise…”. I think you could probably combine the entire noise submenu from that tree, and make it instead a segmented control on the actual “noise” dialog that chooses your type of noise. I suspect dropping the “render” level as well would also be good. “Render” is a bit of a jargon-y term in the context of graphics editing, and I don’t think it means much to most people using it. Furthermore, the top “filter” menu isn’t actually all that long, and people generally prefer wide flatter trees to narrower deeper trees. So, I’d pitch for a simpler menu that would just be “filter->noise…”. By flattening and combining, I think that menu could be made much more usable and discoverable.