In result to the ticket "How to use IXFEntityExtension for Many to Many" , everything is working fine but it's not possible to have the extension in Detail View without to run the App.
Please see the attachment.
Sorry for the delay with the answer.
You must add the extension to Detail View yourself through the Model Editor. (See Add an Editor to a Detail View)
Feel free to contact us if you need further assistance or have additional questions.
Regards, Mariya On behalf of Xafari Client Services Team
Working fine now!