This works great, except that every trade is one emerald for one item.

`{"customCategories": {
"extra_goodies": {
"name": "Playing with Trains! Extras!",
"icon": {
"item": "minecraft:creeper_head"
}
}
},
"customEntries": [
{
"output": {
"item": "minecraft:fern",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:dead_bush",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:sea_pickle",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:brown_mushroom",
"amount": 4
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:red_mushroom",
"amount": 4
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:chorus_plant",
"amount": 2
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:end_stone",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:glowstone",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:tube_coral_block",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:brain_coral_block",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:bubble_coral_block",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:fire_coral_block",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:horn_coral_block",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:tube_coral",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:bubble_coral",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:fire_coral",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:horn_coral",
"amount": 16
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:tube_coral_fan",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:brain_coral_fan",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:bubble_coral_fan",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:fire_coral_fan",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:horn_coral_fan",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:bamboo",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:cocoa_beans",
"amount": 4
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:nether_wart",
"amount": 4
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:crimson_fungus",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:warped_fungus",
"amount": 8
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
},
{
"output": {
"item": "minecraft:creeper_head",
"amount": 1
},
"payment": {
"item": "minecraft:emerald"
},
"category": "extra_goodies"
}

]
}
`

Needs to be count, amount was only supported in entryOverrides and has since also been deprecated in favor of count.