Add & remove exercise to exercise collections
Go to the menu item "Training Ground" and click on "Database".
Now click on the collection button of the respective exercise, to add the exercise to an existing collection.
You can now add the exercise to a collection, by clicking on its name.
The blue check mark next to the name shows that this exercise is already part of the respective collection.
Now click on this collection to remove the exercise from it. Following, the collection now appears without the blue check mark.