Custom Villagers

I think you should make a mob with a villager model.

Next make a GUI, see the example of mcreator of the "Fusion table", it can help you to make the trade.

Make a procedure that open the GUI and put it in the event of the mob of "when right click".

I hope its helpful for you.

Make a procedure that only has the [Open GUI for Provided Player, GUI:] brick. Select your custom villager's GUI.

Next on the When Mob Right Clicked option, place that procedure.

In case you didn't know: the When Mob Right Clicked drop down is on the page that you make your mob.

IK this Post Is Old But i Figured out one way of Making Custom Villagers

Using This Reddit post  https://www.reddit.com/r/feedthebeast/comments/cbgxvw/vanilla_villagers…

And This Comand Genorator 

https://www.digminecraft.com/generators/villager_trade_1_17.php

I was able to make this code for The Mod Gr33n's Magica 

I am thinking of adding in a vilager you summon some how by making a procedure run this cmd (on the server side i think)

/summon villager ~ ~1 ~ {VillagerData:{profession:toolsmith,level:5,type:plains},Invulnerable:1,PersistenceRequired:1,Offers:{Recipes:[{buy:{id:"greens_magica:magic_card",Count:64},buyB:{id:"greens_magica:energy_card",Count:64},sell:{id:"greens_magica:smite_curse",Count:1},maxUses:9999999}]}} 

you can add more trades if you want as well

You can actully make villagers trade modded items by using "parentheses"  keep in mind it is case sensitive 

if I am making a villager what "mob natural spawning type" should I put so it spawns in villages

This is very old now there is 'custom villager profession' creator.

hello, still need help?