In non-pinned mode, the hierarchy panel remembers which game objects you've expanded to look at their child objects.
In pinned mode, the hierarchy panel does not remember.
1. start with your hierarchy reduced by clicking the triangle next to the scene name for example
2. put Peek in non-pinned mode
3. open your hierarchy panel and expand/hide various game objects
4. close the hierarchy panel
5. reopen it and it remembers what you expanded/hid
6. put Peek into pinned mode
7. open the hierarchy panel again and expand/hide various game objects
8. close the hierarchy panel
9. reopen it and it does not remember what you expanded/hid
Customer support service by UserEcho