You can automatically hide the fields using inverse_of like this
class Entity < ActiveRecord::Base
# Associations
has_many :contacts, inverse_of: :entity
accepts_nested_attributes_for :contacts, allow_destroy: true
end
class Contact < ActiveRecord::Base
# Associations
belongs_to :entity, inverse_of: :contacts
end
If you set the :inverse_of option on your relations, RailsAdmin will automatically populate the inverse relationship in the modal creation window. (link next to :belongs_to and :has_many multi-select widgets)
Source: https://github.com/sferik/rails_admin/wiki/Associations-basics
Let me know how it went