For example, suppose you click: communities » All and then query:

tech -site:lemmy.world

in the world of web searches, that would look for “tech” but it would exclude results on lemmy.world. I see no way to do this. In general, there are certain instances that folks might prefer to avoid. Seeing an imbalanced ocean of links flooding in from a giant node isn’t useful if we are actually looking for less central communities.