Heal entity when player right clicks it with a specific item

In terms of taming, as well as breeding for that matter. I think it automatically sets the taming item to heal the mob.
But, if not, and in more general terms, while editing the entity, under "Triggers" there should be a spot that says "When right clicked on entity". Should be in the center of the screen
 

Simply make a procedure that checks if the item in the main hand of the player is the right item, then have it heal the entity. Probably by giving it instant_health for a short second. Use "Source Entity" as the player and "Event/Target Entity" as the entity being right clicked. 

Hm, Not too sure if I know a way then. You could possibly use a couple of the "Execute command" procedure blocks in the world management section. With commands like

execute as entity @p[limit=1,nbt={SelectedItem:{id:"minecraft:chicken",Count:1b}}] run clear @s chicken 1 | to remove a raw chicken from the player.

And

execute if entity @p[limit=1,nbt={SelectedItem:{id:"minecraft:chicken",Count:1b}}] run effect give @e[distance=0..0.01] instant_health 20 1

To heal the entity if the closest player is holding raw chicken when right clicked (Though, this would also allow for another player to be holding chicken and then a different player could activate it for them)

Im not exactly sure how well this would work, if at all. But I think it might.
I also mightve made mistakes in those commands themselves, but yeah. I think the way to go with this may be command based.

Maybe https://mcreator.net/plugin/64513/minecraft-1122-generator, not sure if it supports this feature, though