Yes, Loopio does keep track of how many times your Library Entries have been used, and will also display the Projects that the Entry has been used in.
How Do I View The Times Used Feature?
This information is stored in your Library on the right of the Entry. When you access your Library, you can navigate to the right of the Entry, and you will see "Used X times".
You can then click on the number of times used, and this will display the Projects that the Entry has been used in. This displays the Project name, and the date the Project was created.
Note: This list will be ordered by the date the Projects were created, with the most recent in the first position.
You will also find this functionality while doing a Library Search within a Project:
Can I View The Entry From The Times Used?
Yes, you're able to select a Project from the list and it will open it in a separate browser tab with the Project Entry in focus View.