To enter a blank line into a document press. The key without typing any text on the line

Enter key. And do not type any text on the line.

Explanation:

You need to type the enter key, and without typing any of the text on the line. You can use this method to increase the cell size of the table as well, and wherever, you need to enter a new line. And you cannot code here or using any other command as respectively you are on front end UI like a word processor or text editor, and not code editor, and really you don't have any other command available as well.