How create custom action button on sharepoint online command bar without spfx?

I'm creating a provider hosted add-in for sharepoint online and i want to create button or, better if possible, a dropdown button in the command bar, somthing like this:

maybe this question has been asked many times but i can't find any clear answer.

So far i could create buttons inside the context menu of the items creating custom actions with visual studio.

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <CustomAction Id="2bd189ad-3561-405e-815e-39f1a7fa1548.MenuItemCustomAction2"
                RegistrationType="List"
                RegistrationId="101"
                Location="EditControlBlock"
                Sequence="10001"
                Title="Invoke &apos;MenuItemCustomAction2&apos; action">
    <!-- 
    Update the Url below to the page you want the custom action to use.
    Start the URL with the token ~remoteAppUrl if the page is in the
    associated web project, use ~appWebUrl if page is in the app project.
    -->
    <UrlAction Url="~remoteAppUrl/WebForm1.aspx?{StandardTokens}&amp;SPListItemId={ItemId}&amp;SPListId={ListId}" />
  </CustomAction>
</Elements>

but i can't find a similar one for the command bar. I'm not using sfpx because, as far as i understand, it is just for sharepoint hosted applications.

Thanks for helping.

@alejandro Guevara,

You can use PnP provisioning engine and custom action to add a dropdown command bar into the library page.

• CommandUI.Ribbon user custom actions

BR