The feature called "bookmarks" was recently completely overhauled by Stack Exchange and it is now called saves:
- Bookmarks have evolved into Saves
- Recent feature changes to Stack Exchange - October 2022
- Help Center: How do I use saves?
One of the changes is that now you can organize your saves to several lists and give them any names you wish. And you can also add a private note to each of the saved posts.
You can find some other useful links in the corresponding tag-info both on this meta and on Meta Stack Exchange.