The spreadsheets follow a set of rules. They are not free-form, each cell or row or column has certain meanings and restrictions.
Column D is reserved, along with all columns up to J. Columns K and beyond can be used for random comments, columns before that cannot contain text that is not in one of the "validation" lists, like outputs, inputs, function names. The red arrow and message are the spreadsheet trying to indicate an error condition.
The spreadsheet code and the quadstick try to protect the quadstick from bad data in these locations, which is why you sometimes see working configurations with content in those cells, but that is just luck.
The touchpad has attributes of both a button and a joystick. Most of the time it is used just as another button, but it can be used in other ways.