Add custom button in document library item Display Form

Question

I am trying to add a custom button in the display form for a document library item. I managed to do it for Display form for a list item, but can't adapt it to a document library item, anyone have ideas what is needed to be change in order to work for document library item? I believe something in the Location attribute should be changed, but not sure in what way. Below you can see sample for the list item.

<CustomAction
Description="Search Title on Bing"
Title="Bing It!"
Id="{E538E8C7-65DA-454E-AD87-4A603B6CC569}"
Location="CommandUI.Ribbon.DisplayForm"
RegistrationId="100"
RegistrationType="List"
Sequence="0"
Rights="ViewListItems"
xmlns="http://schemas.microsoft.com/sharepoint/">
<CommandUIExtension xmlns="http://schemas.microsoft.com/sharepoint/">
<!-- Define the (UI) button to be used for this custom action -->
<CommandUIDefinitions>
<CommandUIDefinition 
Location="Ribbon.ListForm.Display.Manage.Controls._children">
<Button Id="{B511A716-54FF-4EAE-9CBE-EA02B51B626E}"
Command="{4E2F5DC0-FE2C-4466-BB2D-3ED0D1917763}"
Image32by32="_layouts/15/images/placeholder32x32.png"
Sequence="0"
LabelText="Bing"
Description="Search Title on Bing"
TemplateAlias="o1"
/>
</CommandUIDefinition>
</CommandUIDefinitions>
<CommandUIHandlers>
<!-- Define the action expected on the button click -->
<CommandUIHandler 
Command="{4E2F5DC0-FE2C-4466-BB2D-3ED0D1917763}"
CommandAction="javascript:openDialog(); 
function openDialog() { 
alert('Hello');      
}; 
}
"/>
</CommandUIHandlers>
</CommandUIExtension>
</CustomAction>
</Elements>

Answer 1

Yes you are right it with the Location attribute and according to you snippet Location="CommandUI.Ribbon.DisplayForm" means that a button will be added on display form. And Location="Ribbon.ListForm.Display.Manage.Controls._children" of CommandUIDefinition specifies that it will be added to the Manage tab of the Display form.

To change the custom action to appear on document library view you should try with CustomAction Location to CommandUI.Ribbon.ListView and in CommandUIDefinition set Location="Ribbon.Tabs._children"

Answer 2

I managed to make it. In the registrationID I set the contenttypeID which I am using and in RegistrationType I changed it to be ContentType. This did the trick! Here is a working sample:

<CustomAction
Description="Search Title on Bing"
Title="Bing It!"
Id="{E538E8C7-65DA-454E-AD87-4A603B6CC569}"
Location="CommandUI.Ribbon.DisplayForm"
RegistrationId="IdOfTheContentType"
RegistrationType="ContentType"
Sequence="0"
Rights="ViewListItems"
xmlns="http://schemas.microsoft.com/sharepoint/">
<CommandUIExtension xmlns="http://schemas.microsoft.com/sharepoint/">
<!-- Define the (UI) button to be used for this custom action -->
<CommandUIDefinitions>
<CommandUIDefinition 
Location="Ribbon.ListForm.Display.Manage.Controls._children">
<Button Id="{B511A716-54FF-4EAE-9CBE-EA02B51B626E}"
Command="{4E2F5DC0-FE2C-4466-BB2D-3ED0D1917763}"
Image32by32="_layouts/15/images/placeholder32x32.png"
Sequence="0"
LabelText="Bing"
Description="Search Title on Bing"
TemplateAlias="o1"
/>
</CommandUIDefinition>
</CommandUIDefinitions>
<CommandUIHandlers>
<!-- Define the action expected on the button click -->
<CommandUIHandler 
Command="{4E2F5DC0-FE2C-4466-BB2D-3ED0D1917763}"
CommandAction="javascript:openDialog(); 
function openDialog() { 
alert('Hello');      
}; 
}
"/>
</CommandUIHandlers>
</CommandUIExtension>
</CustomAction>
</Elements>