Hello @BarryF02 ,
What are you referring to when you say "subject block?" The subject line of an email can be edited by clicking in the top area with the subject line, from name, from email, etc. while editing the email. If you're referring to an action block such as a text block, image block, poll block, one of the various layout blocks, etc. you can find those in the left-hand menu while building your email.