app/controllers/spree/admin/users_controller_decorator.rb
Spree::Admin::UsersController.class_eval do
def subscriptions
params[:q] ||= {}
@search = Spree::Subscription.ransack(params[:q].merge(user_id_eq: @user.id))
@subscriptions = @search.result.page(params[:page]).per(Spree::Config[:admin_products_per_page])
end
end