When choosing the “Single Post (A Single Full Post)” block, there’s a drop down menu showing the last (by date) 100 or so posts. How do I select a non-listed (e.g. older) post?
single post block drop down picker is limited to the last 100 posts. To send a newsletter with an older post, I’d recommend to install Instasend addon, open up the desired post and create an Instasend newsletter from the sidebar.