This animation best describes the pattern, whereby a new row in the table is always preserved so that the user can insert a new row without clicking a +
button or similar:
Does it have a name? At my company we call it the 'ghost row'
The particular one that you have mentioned in the question do not have a name by definition as of now it seems. Anyways, from a technical side it is Adding rows dynamically with jQuery. Therefore maybe we can call it Dynamic New Row. [from today haha]
Please post your answers if it actually has a defined name. Then I shall remove my answer :)
Also, I'm posting this StackOverflow link to the technically analogous question.
template row