How to add a bookmarking feature?

I would like to integrate a bookmarking button on every page of my training, with which the user can tag slides - for example, to review them in more detail at a later time. The bookmarked pages should be listed in a dropdown menu or highlighted in the TOC. It is not necessary to store the information in the LMS. I only need the bookmarks during the current training session. They may be forgotten when the training is closed.

Is it possible to implement such a function using variables?

Thank you for any ideas!