If you have more than one "library" available to you in Sora (examples: belong to the MLS Sora Commonwealth eBook Collection program, have a separate collection for your district, and also have a public library card connected), you can switch and toggle between the different collections/libraries.
To switch to another library, go to the settings menu (click on 3 horizontal lines in top-right corner) and scroll down to view your list of libraries. There will be a checkmark on the library whose collection you're currently viewing. Choose a different library's collection to select it. You can toggle back and forth to view the collection of your different libraries.
TIP: While it is not possible to see all of your libraries' collections at the same time on the Sora "Explore" page, it IS possible to include all of your available collections when doing a search. To turn on this feature, go to the settings menu (click on 3 horizontal lines in top-right corner), scroll down and click on "All Settings" then scroll down under "General" to turn on the "Search All Libraries" option. When this option is checked, you can search all of your available libraries for an author or title.