Hello, Fabrizio,

By default, RadGridView allows you to copy multiple rows data and paste them to the data rows. Note that one of the data rows should be current. However, RadGridView is not supposed to perform copy/paste operation inside the new row and insert new records this way.

However, you can easily achieve it by customizing the default paste action in the MasterGridViewTemplate.Paste method. You can refer to the following forum post demonstrating a sample approach: https://www.telerik.com/forums/paste-from-excel-in-to-add-new-row

We already have a similar feature request logged in our feedback portal. You can track its progress, subscribe for status changes and add your comments on the following link - https://feedback.telerik.com/winforms/1372364-add-radgridview-add-paste-operation-in-the-new-row

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik