@Julenaworld
the default is {{ first_name|default:''|capfirst }} which will take persons name from your account and use it instead.. but in case the subscriber doesn’t have a name in your klaviyo account you can use some word to use that instead if the name is not available..
People usually use Customer or Friend or something like that.. and the code for that is simple for example {{ first_name|default:'Friend'|capfirst }}.. whatever you like the word to be just add it between '' in the code.. so in this case.. if subscriber has a name this code will use their name and if they don’t have the name it will say Hi Friend instead..