Adding A “Read More” Link
Use a read-more link to focus on your lead sentences, then link readers to the full-version on your blog. Read-more links can go into the text or caption for any post type, except for chat posts.
1. When using the rich-text editor, identify a spot in your text for the break. Place your cursor there and press the enter key to add a new blank line.
2. A circled plus-sign icon will appear to the left. Click the plus sign, and four icons will appear.
3. Click the fourth icon — the gray bar with three white dots — to add a read-more link.
4. Tumblr inserts a “Keep reading” line. The read-more link is in place.
5. Publish the post — or queue, schedule or save as a draft.
Update: Tumblr has a keyboard shortcut for the read more link. While in the post form, press Command + Shift + K (Mac) or Ctrl + Shift + K(Windows).
Credit goes to unwrapping Tumblr for creating this guide.