Add custom action to the ribbon as submenu of a button

Question

I have a question regarding how to add a custom action to the ribbon as a part of a sub action of existing button. I think the screenshot will make it clear:

So i would like to add a custom action behind this "New Item"? Is this possible and how to do that? What is the location?

If this is not possible how do I add, then nex to it?

PS: could anyone give a good site where i can find all the possible locations where to add custom actions?

  <CustomAction
     Id="AddMultiple"
     RegistrationType="List"
     RegistrationId="202"
     RequireSiteAdministrator="FALSE"
     Location="CommandUI.Ribbon"
     Sequence="10001"
     Title="Multiple Add"
     Description="">
      <CommandUIExtension>
        <CommandUIDefinitions>
          <CommandUIDefinition Location="Ribbon.ListItem.New.Controls._children">
            <Button
              Id="Ribbon.ListItem.New.AddAttendees"
              Sequence="5"
              Command="Add"
              LabelText="Multiple Add"
              ToolTipDescription=""
              TemplateAlias="o1" />
          </CommandUIDefinition>
        </CommandUIDefinitions>
        <CommandUIHandlers>
          <CommandUIHandler Command="Add" CommandAction="javascript:" />
        </CommandUIHandlers>
      </CommandUIExtension>
    </CustomAction>

But this adds to the group and not under the New Item :(

Answer 1

Extending the ribbon is documented on MSDN: http://msdn.microsoft.com/en-us/library/office/gg552606%28v=office.14%29.aspx

It is much simpler to extend the New Item button however. The New Item button will automatically show an entry for each Content Type added tot he list/library.

1. Navigate to List Settings
2. Click Advanced Settings
3. Allow Management of Content Types
4. Add Content Types to the list
5. Arrange the Content Types in your desired order via the link "Change New Button order and default content type" that is displayed below the list of content types.