Shortcut to Insert a Line in a Grid/Table
Just about any screen that has a table/grid, you can quickly add a line by double clicking the grey box in the upper left corner. For those users that use a mouse more than the keyboard, this can keep you focused on the lines and not looking for the icon in the toolbar. Yes, keyboard shortcut (Ins) works great for those user that prefer a keyboard over a mouse.
BTW, you can double click the square to the left of the line number to mark a line to be deleted.