Mylio is designed to run as a single instance of your library on each machine, this means there can not be multiple Mylio libraries within the same user on a single machine.
If you would like to run multiple copies of Mylio on the same machine, you can do so from within separate users. Please note that each user will count as a “device” towards your device limit and take up the space needed to store your images, possibly duplicating the space needed to house your photos. Additionally, since Mylio uses peer-to-peer syncing, you will need at least one additional device set up as a Mylio account to populate the second user. Generally, it is best practice to use an external hard drive as a secondary device that can hold your originals when switching between users.
Below are links to support material from Apple and Microsoft for setting up new users on different operating systems: