app/views/rails_admin/main/new.html.erb
<%= rails_admin_form_for @object, url: new_path(model_name: @abstract_model.to_param), as: @abstract_model.param_key, html: { multipart: true, class: "main", data: { title: @page_name } } do |form| %>
<%= form.generate action: :create %>
<% end %>