Replacement Code Defaults
To provide a default value for a replacement code that does not return anything, use the following syntax.
{replacement::deafult}
For example, to provide a default for the first name of a contact you can use {first::there}
which will output "there" if the first name is not available.
You can also use this for custom meta replacements, for example, you can use {_my_custom_meta::custom_value}
to output "custom_value" if the metadata is not available.