If you upload, and if the post has [attachment=n] where n is 1, then that string will mark the point where the associated attachment displays, replacing the string. Although, for formatting simplicity, the attachment always displays centered on a line by itself. (Attachment=1 can be abbreviated Att=1)
Any attachments that are not mentioned in the post in this way appear at the top as they previously did.
Note: You can only inline an individual attachment once in the post body, so the maximum number of inline attachments displayed is limited to the number of attachments you upload.
When constructing your post, make reference to the attachments where you want them, as in this example:
Note: If you want to replace the attachment in your post, you will need to edit the post first to remove the att=x segment, then continue.