The reason why it's worth putting some words in ‘your saved words' when developing your vocabulary is that some words are more stubborn, harder to retain. Regular repetition will help you to memorize and use these words more quickly and effectively in practice.
From ‘your saved words', you can create your own personalized list of only the words you think are important. This can be a simple and effective way to learn words, as you can easily access and review these expressions whenever you want to repeat them.
If you want to add a word to ‘your saved words’, all you have to do is click on the heart icon on the selected word card or in the vocabulary list!