Previous Post Block
The Previous Post Block will display a navigation link for the Post that precedes the current Post. This Block is only useful for Posts, not Pages, and although you can add this block into your normal Post content, it will be more useful once you can edit your Theme’s templates. The link that this Block produces is typically seen at the bottom of Single Posts and allows you to navigate to the previous Post. It’s different to the Navigation links that you typically see on your main Blog Archive page (i.e. the page that shows a list of your current Posts).
Once you've added the block, there are further options available in the Settings Sidebar. Clicking on the Transform to variation dropdown, allows you to switch this block with the Next Post Block, which shows a link to the next Post.
You can also change various Typography settings like Font size, Appearance, Line height, Letter case & Letter spacing.