Florian TIAR

This plugin add a margin note to your content. 
For example, if you want to add a source to your post, you can use the shortcode. You will see a margin note in the left of your content when you hover the desired text.
This plugin use the following open source javascript library by Francisco Dans : https://github.com/fdansv/marginotes
If you want to contribute to this plugin, feel free to check the Github repository : https://github.com/Mahjouba91/wp-margin-notes

WP Margin Notes

Simply add margin notes to your content (pages, posts or CPT) just by using the [margin_notes] shortcode

Jason Yingling

bonaparte

Jeremy Varnham

WP Reading Time let’s you easily add an estimated reading time to your WordPress posts. Activating the plugin will automatically add the reading time to the beginning of your post’s content. This can be deactivated in the Reading Time settings which can be accessed from your Dashboard’s Settings menu. You can also edit the label and postfix from this menu.
If you’d prefer more control over where you add your reading time you can use the the [rt_reading_time] shortcode to insert the time into a post. This shortcode also excepts values for label and postfix. These are optional. Ex. [rt_reading_time label=”Reading Time:” postfix=”minutes” postfix_singular=”minute”].

Reading Time WP

This is awesome

Easy to setup and get shortcode added. Done in minutes

Just what I needed

Reading Time WP creates an estimated reading time of your posts that is inserted above the content or by using a shortcode.

WP Margin Notes vs Reading Time WP