Open-DSI

Courses will have a new tag to set their Degree of Difficulty. You can choose between 3 predefined options: Beginner, Intermediate and Advanced. 
You can add, edit or remove your own degrees of difficulty by going to “Courses > Degrees of Difficulty” from the menu.
Upload and display an image (or icons, pictograms) for your degree of difficulty (thanks to John James Jacoby and his <a href="https://wordpress.org/plugins/wp-term-images/" rel="ugc">WP Term Images</a> plugin!).
Degrees of Difficulty can be displayed by your theme using the <code>dds_get_sensei_course_degrees_of_difficulty()</code> function.

Degree of Difficulty for Sensei

Sensei LMS add-on to set and display the degree of difficulty of a course.

Patrick Sletvold

The Difficulty Taxonomy plugin adds a basic taxonomy for sorting posts into different difficulties. Currently it offers a way to create and edit difficulties, and assing them to posts. At the moment, this plugin does not handle showing the difficulties in the theme, however support for this is to some extent planned for the future

Difficulty Taxonomy

The Difficulty Taxonomy plugin adds a basic taxonomy for sorting posts into different difficulties.

Degree of Difficulty for Sensei vs Difficulty Taxonomy