Dynamics crm2013 1: n relation sub-grid "add existing item" and "Add new item"

In crm2013, the sub-grid style and 2011 have greatly changed. The comparison between 2013 and 2011 is as follows:

At 2011, the button is in the ribbon area. For the 1: N parent-child relationship entity, click Add new record, but 2013 won't work. Click the plus sign. First, there will be a drop-down box listing the existing child body data. You can select the existing one or create a new one.

Since your relational entity is a 1: N parent-child entity, the existence of the child must be dependent on the parent entity, therefore, there will be no association with existing entities in this place, and an error will be reported once the association is made. Therefore, the steps here will be cumbersome if the creation is broken down, and it will also confuse users.

Therefore, in this case, there is no need to add existing records. How can this problem be removed? You only need to set the field as necessary when creating a link, after the settings are complete, return to sub-grid and click the plus sign to bring up the new page instead of the drop-down box.

When you enter the child body view in the navigation bar, only the buttons for adding new items are left, and no buttons for adding existing items are available.

Is the display of "Add new item" and "add existing item" caused by different levels of field requirements in the query field in various links