At the moment, you can only connect multiple Google Calendars that are shared with you.
To select / unselect certain Calendars from showing up in your Limitless Meetings overview:
Click the 3 dots in the top right corner > Show Calendars
Another option: click on Google (on the left side under "Connections") and look for "Show calendars"
Vote on our feature request board to add multiple inboxes, and integrate with other types of calendars (Outlook/Microsoft 365/Apple/etc).
A hack for Apple/iCloud Calendar users, check out this article to link your Apple/iCloud Calendar to Google Calendar (thank you Maclean Dunkin for sharing!).