It is not possible to mark the trailhead module "Creating and Customizing Lightning Apps" as "read". There is no challenge required, and it says "This unit doesn't have a challenge. You can still earn points by marking the unit as read. Good job!". So, to complete the module, it must be marked as read. I am logged in, and still unable to mark as "read". What am I missing?
Cheers,
Henk

It is not possible to mark the trailhead module "Creating and Customizing Lightning Apps" as "read". There is no challenge required, and it says "This unit doesn't have a challenge. You can still earn points by marking the unit as read. Good job!". So, to complete the module, it must be marked as read. I am logged in, and still unable to mark as "read". What am I missing?
Cheers,
Henk

I do not see any option on the page, however the challenge section says that 'This unit doesn't have a challenge. You can still earn points by marking the unit as read. Good job!' 
This is for Creating and Customizing Lightning Apps trail.