That is most definitely possible. In principle, you can link an infinite number of websites to just one account. However, all these websites must belong to one and the same company and so fall under the same Chamber of Commerce registration number.
Would you like to link a second website to your account? Then please go to the option 'website profiles' in your account and click on the 'New website profile' button. When creating an account for Mollie, you can first only add one website profile and add extra website profiles later on.
Creating a new website profile is possible via settings and website profiles, not by clicking on 'Create new organization' below your company name on the top left. You can, for example, click on this when you would like to add an extra company to your account.
See for more information about setting up your Mollie account: How do I sign up for Mollie?