From FilterBlade FAQ I saw these instructions:
I want to show/hide ALL items of a certain type or a specific item. How do I do that without editing entire sections of the filter?
A: Adding custom rules to the filter is the perfect solution for tasks like this.
Simply go to one of the custom rule section in the Customizer (there is one for endgame rares, one for leveling and one in the Misc. section for everything else).
There, you can add Show and Hide rules for specific BaseTypes, Item Slots (like Rings or Two-Hand-Axes), etc.
You can add additional filtering for ItemLevel, Rarity & Co.
The strictness of the rule determines how many of the existing rules it will overwrite.
The "Add Misc Rule" has no way to tick rare+unique.
I can't feasibly use on of the other rules (e.g. BaseType) as I'd have to select every single type to get the same effect which seems wrong.