Hello,
here in this screen: 
I should be asked to which deck i want to add the vocabulary. so i can make a deck called Pleco to use that for all my vocabulary that i want to import in Pleco.
 
      
    Hello,
here in this screen: 
Hello Markus,
Thank you for the suggestion. I just tried to add the vocabulary into my deck and it did not ask me to choose a deck, which can be quite inconvenient. I’ll forward this to the developers.
Rebecca