Use the "optional" settings on a step to give the learner the ability to "skip" over certain assignments that are supplementary or to provide multiple ways to complete an assignment.
While on the Path tab of your course, either in the Master or with the “Edit” button switched on, select a step and then select Settings (the gear icon in the upper right corner).
One of the options here is the "Require completion" toggle button.
If you toggle this button on (the default), learners will need to complete the step in order to finish the class and receive completion status.
If you toggle the button off, the step will be marked as "optional." Learners will be able to skip the step and still receive completion on the class.
Note: this setting should only be used for selected steps that are truly optional. Please do not set all steps in the course to "optional." At minimum, the last step in your course should be set to "required." When the last required step is marked complete by the user, the entire course will register as completed, and if you have provided a certification of completion, it will become available at this point.