You cannot 'split' a cell into 2, unless it is a previously merged cell.

If you provide more detail about your ultimate objective, you might get
advice on an alternative approach


"Chalky" wrote:

I am working in a spreadsheet where I frequently use the filter and sort
functions. I want to split one cell into two in one column, I don't want to
use two columns and merge the rest of the cells as this upsets the
filter/sort functions.