A tree shortcut is when you use the test out option for a specific checkpoint. If you pass the test (in other words, you don't lose more than three hearts), all skills leading up to that checkpoint will be marked as completed. If you lose four hearts, you won't pass the test, and if you continuously lose four hearts while testing out multiple times, you'll lose the ability to test out.

As shown in the screenshot I've provided, fourteen uncompleted skills are leading up to this specific checkpoint. Using the test out option would allow me to skip these skills, and they would also be marked as completed.

Once you've progressed past a certain checkpoint, there won't be a test out option anymore, and it will just be labeled as "checkpoint passed".

It's when you test out of skills; you don't do the skills one by one but you do it in one task in which you have hearts. If you lose 4 hearts, you only have a few more opportunities to test out without losing all the hearts.

Thank you. This made it very clear. I tend not to test out but work through the tree as it comes. So I guess I am safe. I have been away from my tree for sometime so re-building it to Gold.