I want to Migaration AttachObject.

I used the Suite 4.0 version before.

The function used at that time is Layout.AttachObject.

In Suite7.0, it has been confirmed that the AttachObject function has been removed.

How should I solve it??

You may attach any html content to your layout cell using the attachHTML method:
https://docs.dhtmlx.com/suite/layout__api__layout_attachhtml_method.html
So you can attach any html container to your layout cell.