I'm trying to blacklist certain items from enemy use using moffein's blacklist but it doesn't work using the ingame names. I tried finding the code names in the console but couldn't find them. 

Would you mind providing a list of the code names for the respective items?

Sure!

Common:
MysticsItems_HealOrbOnBarrel - Donut
MysticsItems_ScratchTicket - Scratch Ticket
MysticsItems_BackArmor - Spine Implant
MysticsItems_Manuscript - Manuscript
MysticsItems_LimitedArmor - Cutesy Bow
MysticsItems_Cookie - Choc Chip
MysticsItems_MarwanAsh1 - Marwan's Ash

Uncommon:
MysticsItems_CoffeeBoostOnItemPickup - Cup of Expresso
MysticsItems_ExplosivePickups - Contraband Gunpowder
MysticsItems_AllyDeathRevenge - Vendetta
MysticsItems_Spotter - Faulty Spotter
MysticsItems_SpeedGivesDamage - Nuclear Accelerator
MysticsItems_ExtraShrineUse - Black Monolith
MysticsItems_KeepShopTerminalOpen - Platinum Card
MysticsItems_MysticSword - Mystic Sword
MysticsItems_Rhythm - Metronome
MysticsItems_ElitePotion - Failed Experiment
MysticsItems_DroneWires - Spare Wiring
MysticsItems_DeathCeremony - Ceremony of Perdition

Legendary:
MysticsItems_Voltmeter - Wireless Voltmeter
MysticsItems_ThoughtProcessor - Thought Processor
MysticsItems_CrystalWorld - Crystallized World
MysticsItems_DasherDisc - Timely Execution
MysticsItems_TreasureMap  - Treasure Map
MysticsItems_Idol - Super Idol
MysticsItems_Backpack - Hiker's Backpack
MysticsItems_VyraelCommandments - Ten Commandments of Vyrael
MysticsItems_JudgementCut - Devil's Cry

Lunar:
MysticsItems_RiftLens - Rift Lens
MysticsItems_Moonglasses - Moonglasses
MysticsItems_RegenAndDifficultySpeed - Puzzle of Chronos

You can also check out the `en.language` file in the mod's folder to see the codenames of the items, in case the mod ever gets updated with new content. They will be in all caps there, though, so you'll need to match them against case-sensitive item names in https://github.com/TheMysticSword/MysticsItems/tree/main/Items

Thanks! Appreciate it. And thanks for the extra lesson ^^