Loot Table Modification (WIP)

onEvent('block.loot_tables', event => {
  event.addSimpleBlock('minecraft:dirt', 'minecraft:red_sand')
})

onEvent('block.loot_tables', event => {
  event.addSimpleBlock('minecraft:dirt') // To drop itself (fix broken blocks)
  event.addSimpleBlock(/minecraft:.*_ore/, 'minecraft:red_sand') // To drop a different item
})

onEvent('block.loot_tables', event => {
  event.build('minecraft:dirt', table => { // Build loot table manually
    table.pool(pool => {
      pool.rolls = 1 // Use one of these 3 - fixed, uniform, binominal
      // pool.setUniformRolls(4, 6)
      // pool.setBinomialRolls(4, 0.3)
      pool.survivesExplosion()
      pool.addItem('minecraft:dirt')
      // pool.addCondition({json condition, see vanilla wiki})
      // pool.addEntry({json entry, see vanilla wiki for non-items})
    })
  })
})

Example from FTB Stranded: (adds 1-3 leaves dropped from all Leaves blocks, 4-8 logs from all log and wood blocks and 4-8 stone from Stone, Cobblestone, Andesite, Diorite and Granite)

onEvent('block.loot_tables', event => {
	event.addBlock(/minecraft:.*_leaves/, table => {
		table.pool(pool => {
			pool.setUniformRolls(1, 3)
			pool.survivesExplosion()
			pool.addEntry({type: 'minecraft:item', name: 'ftbstranded:leaf'})
		})
	})

	event.addBlock(/minecraft:.*_(log|wood)/, table => {
		table.pool(pool => {
			pool.setUniformRolls(4, 8)
			pool.survivesExplosion()
			pool.addEntry({type: 'minecraft:item', name: 'ftbstranded:wood'})
		})
	})

	event.addBlock([
		'minecraft:stone',
		'minecraft:cobblestone',
		'minecraft:andesite',
		'minecraft:diorite',
		'minecraft:granite'
	], table => {
		table.pool(pool => {
			pool.setUniformRolls(4, 8)
			pool.survivesExplosion()
			pool.addEntry({type: 'minecraft:item', name: 'ftbstranded:stone'})
		})
	})
})