You can add your own tags on you space cards to organise your library. Read more about space cards here.
How to add tags to your space cards
Go to the space that you want to add tags to. On the right side of the space card, click on the three dots.
After clicking the button, a menu opens. Click on Edit Tags to add tags to your space card.
A pop-up menu opens. Here you can type what you want your tag to say.
Click on Add when you have finished typing. When you have added your desired tags, click on the button OK to save all your tags.
You will now see all of your tags at the bottom of your space card.