Add a filter that bins values includes NULL

I have a field ‘window’ with integer values and nulls. I would like to bin the field for use in a filter e.g. in sudo code:

```

if window filter == 1 then window == 1 || null,

if window filter == “<=3” then window <= 3 || null,

if window filter == “<=10” then window <= 10 || null,

if window filter == “>10” then window  >10 || null,

```

Working on my first Looker dashboard here. I have a single table feeding the view, no joins. I just need to somehow bin the field ‘window’ into the 4 groups above and in each case include null values.

How can I do this?