Variants#index - use prebuilt action

app/helpers/spree/admin/navigation_helper.rb

@@ -369,6 +369,10 @@ def payments_actions
       def stock_actions
         Rails.application.config.spree_backend.actions[:stock]
       end
+
+      def variants_actions
+        Rails.application.config.spree_backend.actions[:variants]
+      end
       # rubocop:enable Metrics/ModuleLength
     end
   end

app/models/spree/admin/actions/variants_default_actions_builder.rb

@@ -0,0 +1,37 @@
+module Spree
+  module Admin
+    module Actions
+      class VariantsDefaultActionsBuilder
+        include Spree::Core::Engine.routes.url_helpers
+
+        def build
+          root = Root.new
+          add_new_variant_action(root)
+          root
+        end
+
+        private
+
+        def add_new_variant_action(root)
+          action =
+            ActionBuilder.new(new_variant_config).
+            with_create_ability_check(::Spree::Variant).
+            build
+
+          root.add(action)
+        end
+
+        def new_variant_config
+          {
+            icon_name: 'add.svg',
+            key: :new_variant,
+            url: ->(resource) { new_admin_product_variant_path(resource) },
+            classes: 'btn-success',
+            id: 'new_var_link',
+            data: { update: 'new_variant' }
+          }
+        end
+      end
+    end
+  end
+end

app/views/spree/admin/variants/index.html.erb

@@ -64,8 +64,18 @@
   <% end %>
 <% else %>
   <% content_for :page_actions do %>
-    <%= external_page_preview_link(@product) %>
-    <%= button_link_to(Spree.t(:new_variant), spree.new_admin_product_variant_url(@product), { icon: 'add.svg', :'data-update' => 'new_variant', class: 'btn-success', id: 'new_var_link' }) if can? :create, Spree::Variant %>
+    <% variants_actions.items.each do |action| %>
+      <% next unless action.available?(current_ability) %>
+      <%= button_link_to(
+        action.text,
+        action.url(@product),
+        class: action.classes,
+        icon: action.icon_name,
+        id: action.id,
+        target: action.target,
+        data: action.data
+      ) %>
+    <% end %>
     <%= button_link_to (@deleted == '1' ? Spree.t(:show_active) : Spree.t(:show_deleted)), spree.admin_product_variants_url(@product, { q: { deleted_at_null: @deleted == '1' ? "0" : "1" } }), { class: 'btn-light', icon: 'filter.svg' } %>
   <% end %>
 <% end %>

lib/spree/backend/engine.rb

@@ -41,6 +41,7 @@ class Engine < ::Rails::Engine
         Rails.application.config.spree_backend.actions[:store_credits] = Spree::Admin::Actions::StoreCreditsDefaultActionsBuilder.new.build
         Rails.application.config.spree_backend.actions[:adjustments] = Spree::Admin::Actions::AdjustmentsDefaultActionsBuilder.new.build
         Rails.application.config.spree_backend.actions[:payments] = Spree::Admin::Actions::PaymentsDefaultActionsBuilder.new.build
+        Rails.application.config.spree_backend.actions.include?(:variants) ? (Rails.application.config.spree_backend.actions[:variants].items << Spree::Admin::Actions::VariantsDefaultActionsBuilder.new.build.items).flatten! : Rails.application.config.spree_backend.actions[:variants] = Spree::Admin::Actions::VariantsDefaultActionsBuilder.new.build
       end
     end
   end

spec/models/spree/admin/actions/variants_default_actions_builder_spec.rb

@@ -0,0 +1,20 @@
+require 'spec_helper'
+
+module Spree
+  module Admin
+    describe Actions::VariantsDefaultActionsBuilder, type: :model do
+      let(:builder) { described_class.new }
+      let(:default_actions) do
+        [:new_variant]
+      end
+
+      describe '#build' do
+        subject { builder.build }
+
+        it 'builds default tabs' do
+          expect(subject.items.map(&:key)).to match(default_actions)
+        end
+      end
+    end
+  end
+end