Block properties:

• material
• materialColor
• hasCollision
• lightEmission
• explosionResistance
• destroyTime
• requiresCorrectToolForDrops
• isRandomlyTicking (?)
• friction
• speedFactor
• jumpFactor
• canOcclude (?)
• isAir (?)
• isValidSpawn (?)
• isRedstoneConductor (?)
• isSuffocating (?)
• isViewBlocking (?)
• hasPostProcess (?)
• emissiveRendering (?)

Item properties:

• category
• rarity
• craftingRemainingItem
• maxDamage
• maxStackSize
• food (?)
• isFireResistant

What about attack_damage, attack_speed, armor, and armor_toughness from https://minecraft.gamepedia.com/Attribute ?

Is this still on the backburner?

This is done, actually, see

https://github.com/KubeJS-Mods/KubeJS/blob/master/common/src/main/java/dev/latvian/kubejs/item/ItemModificationEventJS.java

and

https://github.com/KubeJS-Mods/KubeJS/blob/master/common/src/main/java/dev/latvian/kubejs/block/BlockModificationEventJS.java

Event IDs are item.modification and block.modification ^^

What about attack_damage, attack_speed, armor, and armor_toughness from https://minecraft.gamepedia.com/Attribute ?

I'd recommend opening another issue for this, as these attributes are separate from these other properties, and in some cases dictated by the Item's Tier (which KubeJS does have a wrapper for)