It depends a bit on what you want with those libraries.
PD you work with libraries that form the basis for your video project. The libraries are thus
project libraries.
If you want to be able to select some media for your video from several “libraries” or collections, I think it is wiser to have all your media collected or sorted in Windows folders. E.g. a folder per month, or per event. Given these folders a clear name so that you can find your media back easily when you want you use some for a project and want to include them in your project library.
If you want to collect all the media in one library so that you can create one (part of your) video, then it is certainly possible to work with separate libraries. In that library, the project library, you have all your media ready for use in the timeline. One you have created the video in the time line, you can save the library (and the timeline) as a project. Obviously, you would use a name for the project so that you can recognize it easily.
Once you have a collection of projects, you can e.g. produce those projects into separate videos by using the PD batch mode.
Another option is to include the projects into an overall project, it is possible to insert the complete project into the timeline and create one video from the collection of projects.
In general, I would recommend that you organize your media in Windows folders, in such way that it is easy to find them back. There are people who find it easier to make collections per date, others make event collections. etc.
Hope this answers your question, otherwise let us know what it is you want with the libraries.