mc 1.16.5
CraftTweaker-1.16.5-7.1.0.355.jar
JEITweaker-1.16.5-1.0.1.33.jar
jei-1.16.5-7.7.1.110.jar

jei.zs:
import mods.jei.JEI; mods.jei.JEI.hideCategory("appliedenergistics2.inscriber");
this throws the error ingame

Not sure why its prepending minecraft: onto the category, the category I go from the output of /ct dump jeiCategories

So I just checked in-game.

This is the output of /ct dump jeiCategories

List of all known JEI categories: 
- minecraft:crafting
- minecraft:anvil
- minecraft:blasting
- minecraft:brewing
- minecraft:campfire
- minecraft:fuel
- minecraft:furnace
- minecraft:smithing
- minecraft:smoking
- minecraft:stonecutting
- appliedenergistics2:appliedenergistics2.inscriber
- appliedenergistics2:condenser
- appliedenergistics2:grinder
- jei:information

and using:

mods.jei.JEI.hideCategory("appliedenergistics2:appliedenergistics2.inscriber");

Appears to work.

The reason that it was adding minecraft: to the start was because it is a ResourceLocation, meaning it needs to be modid:path, but when we make it, if there is no modid (no :), it gets defaulted to minecraft.

Please let me know if you run into any other issues :)