Pro Tip: use
CTRL+/ to select all cells in an array formula.
Array formulas are great until you go to edit them. They have the nasty property that you must edit the entire region of the array formula. You are not able to edit a cell in the middle of the array. Nor are you able to delete or clear part of the formula. The fastest way to edit or delete an array formula then is to select the whole thing using
CTRL+/. From there you can hit
F2 to edit the thing or delete to clear it out.
When editing array formulas, there are two other relevant tips: