yEd contains already some features that are similar to your ideas.
To quickly create a new node that is similar to the currently selected one, you can use the Duplicate (Control + D) or Add Child (Control + W) commands. To enter/change the label text, either press F2 or activate the setting Edit Label on Create Node in yEd's preferences (section Editor). Since yEd maintains an appropriate selection, you can repeat this steps as often as you wish without the need to touch the mouse.
To import plain text data like line-based files and tab- or comma-separated files, I propose to convert them to Excel format first and then use yEd's Excel import feature.
Nethertheless, we'll consider these ideas since they are more convenient.