I have used general search commands such as the capitalized AND, NOT, OR. But nothing else is provided. These commands only work for the text description withing the page the workshop item is on. An example would be "fighter NOT RE OR RE2" would work only if it is mentioned in the description.

I wish they'd add a tag for modded, so that way you could search for just modded or just vanilla blueprints.
The advice above about using NOT is the best you can get, though it's not perfect.