Usage
view: view_name {
  filter: field_name {
    default_value: "desired default value"
  }
}
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       Hierarchy 
      
      
      
      default_value | 
    
       Possible Field Types 
      Filter, Parameter
      Accepts 
      A string containing the desired filter value
     Special Rules 
      If an Explore specifies a value for this field in an always_filter  parameter, then that setting overrides the default_value setting 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.