unfortunately, there isn’t any way to make a post with a read more on the mobile app at the current moment. however, you can still do so on the web version of the app within your phone / mobile device’s ingrained web browser.
simply log on to your blog and create a new post ( drop down menu located in the top left corner ). once you have the new post open, type [[/ MORE /]] — without the spaces and ‘ / ‘s — for the read more break then type the rest of your post before posting it. when posted, the read more should be included in the post.
of course when you click the link, it should lead you to the full post on your blog.