Do anyone know how to use it ? 
Should work like v2 endpoints.
$Var = 123 
New-UDDynamic -Content {
   new-UDTypography -Text $ArgumentList[0]
} -ArgumentList $Var 
You shouldn’t have to use it unless you are using an automatic variable that can’t automatically be set in the endpoint.
1..10 | % { 
New-UDDynamic -Content {
   new-UDTypography -Text $ArgumentList[0]
} -ArgumentList $_ }