Usage
view: view_name {
  filter: field_name {
    default_value: "desired default value"
  }
}
| Hierarchy default_value | Possible Field TypesFilter, Parameter AcceptsA string containing the desired filter value Special RulesIf an Explore specifies a value for this field in an always_filterparameter, then that setting overrides thedefault_valuesetting for the field. | 
Basics
The default_value parameter is used to specify a default value for filter fields and parameter fields.
Avoid using
default_valuewithparameterif your data has values that include underscores.
An example of its usage is:
filter: order_region {
  default_value: "Northeast"
}
-
Common challenges
If an explore parameter has a value specified by an always_filter parameter, then that setting overrides the default_value setting for the field.