Yes. Each time you log in with a new account, Dashlane will ask if you would ilke to save it. If you have several accounts saved for the same website, Dashlane will ask you to choose which account you want to log in to.
When you try to create an account on a website for which you already have a credential saved in Dashlane, Dashlane will detect this and remind you that you already have an account. Of course, you can choose to ignore this message and to save several accounts for the same website.
When you visit a website on which you have several accounts, Dashlane will prompt you to select which account you want to log in to.